Good evening! Thank you very much for joining Sports Mole for tonight's crunch match between Chelsea and Porto at Stamford Bridge. Both sides currently occupy a spot in the top two of Group G, but one could well be condemned to Europa League football by the end of this evening, with Dynamo Kiev also in the race if they can beat Maccabi Tel Aviv in Ukraine. It is all to play for for Jose Mourinho against his former side, then, and we should be in for another dramatic night of European action. Let's start with a look at the two teams...

CHELSEA STARTING XI: Courtois; Ivanovic, Zouma, Terry, Azpilicueta; Ramires, Matic; Willian, Oscar, Hazard; Costa

CHELSEA SUBS: Begovic, Cahill, Mikel, Kenedy, Fabregas, Pedro, Remy

PORTO STARTING XI: Casillas; Maxi Pereira, Maicon, Marcano, Martins Indi; Danilo, Imbula, Herrera; Layún, Corona, Brahimi

PORTO SUBS: Helton, Rúben Neves, Evandro, Varela, Tello, Aboubakar, Bueno

What can we make of those two sides, then? Well, the biggest news comes from the Chelsea camp as Diego Costa returns to the starting lineup having been a high-profile absentee in the past two games. The striker was dropped to the bench for the recent clash with Tottenham, and much was made of his bib-throwing antics in that one, while he was also left out against Bournemouth at the weekend. He is back to lead the line tonight, and Mourinho will be hoping for a response from the bullish frontman.

The other big news in terms of returning players comes at the other end of the field, with John Terry back in the starting XI having missed the last two games with an ankle injury sustained on matchday five against Maccabi. The skipper was in and out of the team a little earlier in the season, but he has seemingly established himself as the firm number one choice at centre-back again now and Cahill drops to the bench tonight as a result of his return.

There are two further changes to the side that was beaten by Bournemouth at the weekend, with Fabregas the latest big-name player to be dropped to the bench as Ramires returns from a knock to partner Matic in the deeper midfield role. The Spaniard has been far short of his best this season and is another to have already suffered the wrath of Mourinho. The other change comes at left-back, with Azpilicueta coming back in to replace Baba Rahman.

Elsewhere, Courtois once again starts between the sticks having made his long-awaited return against Bournemouth at the weekend, while further forward there are starts again for Oscar, Willian and Hazard. The latter of those has switched positions a number of times this season, popping up on the left, in the number 10 role or up front, so it will be interesting to see where he is deployed this evening. You'd expect it would be on the left, with Oscar in the middle, but those two can be interchangeable.

As for Porto, they have made three changes to the side that was victorious domestically at the weekend, including something of a surprise omission in the form of Aboubakar. The striker caused Chelsea plenty of problems in the reverse fixture and started on Saturday too, but he has to make do with a place on the bench this evening alongside Barcelona loanee Christian Tello.

The task of leading the line could well fall to Yacine Brahimi instead. He also enjoyed a good time of things when these two sides met at the Estadio do Dragao in September, terrorising the Chelsea defence at times with his direct running and trickery. If he can put in a similar performance tonight then we could well see the end of Chelsea's participation in this season's competition.

If you're looking for experience in the Champions League, you need look no further than Iker Casillas, who racks up yet another appearance in Europe's elite competition this evening. The shot-stopper could well have a point to prove too having been dropped from the Real Madrid team by Mourinho while both were at the Bernabeu - an act that had been almost unthinkable before.

The three men to come in tonight are Marcano, Danilo and Imbula, which suggests that Julen Lopetegui may have one eye on a defensive mindset this evening. They are expected to play a 4-3-3 formation, with Layun - the Watford loanee who scored at the weekend - and Corona flanking Brahimi, who himself can play out wide too.

That is what Chelsea are up against then, and in truth there are no guarantees with the Blues as to whether they will be up to the challenge. Their season is bordering on the status of a write-off already, and failure to reach the knockout stages of the Champions League would leave the FA Cup and Europa League as their only genuine chance of silverware. Capturing either would, of course, be a plus, but it is not how they would have planned their season to be.

The permutations of Group G are all very complicated, and I will go through them in depth a little later, but all Chelsea fans really need to know is that they only need a draw to progress tonight. That would leave them level on points with Porto and potentially Dynamo Kiev, if as expected they beat Maccabi Tel Aviv at home, which means that the head-to-head record will come into play. A win would guarantee top spot and also see them avoid the likes of Real Madrid, Barcelona and Bayern Munich in the next round, while defeat would even be enough should Kiev fail to beat Maccabi.

The Blues currently sit level on 10 points with Porto and two ahead of Kiev having won three of their five group games to date, and the stats certainly suggest that they deserve to progress. They are comfortably the top scorers in Group G with 11 - helped largely by eight in two meetings with Kiev - while they have also conceded the fewest goals, letting in just three in their five European outings this season.

That is a far cry from their domestic form, however, with Chelsea posting the worst defensive figures outside the bottom five just a few months after having cruised to the title on the back of the best record in the division. It has been a remarkable fall from grace for the team, and in particular the defence, but the attack has not fared too much better either. Only five teams in the league have scored fewer than Chelsea's 17 goals this season.

All that leaves them languishing down in 14th place, averaging a point per game from their 15 outings. They have now lost eight matches already this season - more than Mourinho has ever lost in a single league campaign - and find themselves 14 points off the top four with a huge uphill task of hauling themselves back into that race. Indeed, right now the previously unthinkable prospect of relegation seems closer than that, with just two points separating them from that drop zone.

Mourinho has watched his side win just four of their last 14 games in all competitions and lose 11 of their 23 all season. There has been a slight improvement in recent weeks, with Chelsea playing better football and getting a couple of results on the board, but that came grinding to a halt at the weekend with a 1-0 home defeat to Bournemouth in the Premier League. That is the only goal they have conceded in their last four outings, but they have also now failed to score in their past two.

Previously almost unbeatable at home, Chelsea have only won five of their 10 home matches in all competitions this season, losing four in the process. They have, however, won both of their Champions League games here so far this season, while the defeat to Atletico Madrid in the semi-finals of the 2013-14 tournament is their only home loss in this competition in 11 games. Home and away, they have lost only one of their last 13 Champions League games.

It is certainly an impressive record on paper, but Porto will know that there has rarely been a better time to play Chelsea than right now. Lopetegui's side have already beaten tonight's opponents once this season, but they must now do it on foreign soil if they want to guarantee themselves a place in the last 16 of the Champions League following a shock home loss against Dynamo Kiev on matchday five.

Porto are currently level with Chelsea at the top of Group G, but it is they who would miss out on a place in the last 16 should three teams end up level on 11 points. A draw would be good enough for the Portuguese outfit if Kiev fail to beat Maccabi, while victory would guarantee top spot and defeat would see them eliminated unless Kiev fail to win, just like Chelsea.

It could have been a lot less complicated for tonight's visitors if they had overcome Kiev as expected in the last round of fixtures, though. They have won 22 of their last 24 home matches, keeping 18 clean sheets, scoring 59 goals and conceded seven times in the process, which goes to show just how big a shock the loss to Kiev was. It was also their first loss in 10 Champions League home games, during which time they had beaten the likes of Bayern and Chelsea.

They could only manage a 2-0 defeat at the Estadio do Dragao, however, which means that it is all to play for tonight. They are still unbeaten in all competitions away from home this season, though, winning their last five and keeping three clean sheets in a row in the build-up to this match. Their unbeaten record on the road stretches back to 12 games including last season, with their last defeat coming at the hands of Bayern Munich back in April.

Home and away, that Kiev defeat is their solitary reverse in their last 24 games in all competitions, 19 of which have come this season. Again, that run stretches back to the 6-1 defeat at the hands of Bayern in April, but they have responded well to the loss to Kiev, winning their last three games coming into tonight's clash.

Things are going pretty well domestically too, with Porto still unbeaten after 12 games of the Primeira Liga season. They are, however, two points off the top of the table as Sporting Lisbon have also made an unbeaten start to the campaign and sit on 32 points compared to Porto's 30. They have conceded a league-low five goals in the league all season, which is actually fewer than they have let in in their five Champions League games to date.

They were forced to come from behind to get victory at the weekend, with Corona and Layun, both of whom start tonight, getting the goals in a 2-1 victory over Pacos de Ferreira on Saturday. A repeat of that scoreline tonight would see them safely through to the knockout stages as Group G winners.

PREDICTION: We're 10 minutes from kickoff at Stamford Bridge, which means that it is time for a prediction! Chelsea have been very difficult to call so far this season, and if they put in another sub-standard display tonight then Porto are certainly capable of taking advantage. However, the Blues have been a little better in Europe and I expect them to get the point they need to progress tonight. I'll go for 1-1.

The history books certainly point to a Chelsea win tonight, with the Blues having won all five of their previous home games against Portuguese opposition, three of which have come against Porto. Their overall record against Portuguese sides is fairly impressive too, with Chelsea having won nine and lost just two of their 12 meetings.

Porto, on the other hand, have never won in 16 previous visits to England, losing 14 of those and failing to even score in four of their last five trips to these shores. Their victory in September was just the second time that they have beaten Chelsea in seven attempts, while their overall record against English teams stands at 16 defeats, eight draws and seven wins from 31 games.

Andre Andre and Maicon were the scorers when these two sides met in Portugal in September, finding the net either side of a Willian free kick to make it a miserable return for Mourinho, However, the last time these two sides played here at Stamford Bridge, it was Chelsea who emerged victorious as Nicolas Anelka scored the only goal of the game in September 2009.

PERMUTATIONS: Right, I promised you permutations, and here they are. With the prospect of three teams finishing level on points, the group comes down to the head-to-head record between the sides. Kiev have a superior head-to-head record over Porto, but not over Chelsea, while Porto have a superior record over Chelsea. However, Chelsea have amassed the most points in matches between the three sides, which is why they only need a draw to progress, while Porto need a win. Simply put - if Kiev win, then Porto also need to win otherwise they are out and Chelsea and Kiev are through. If Kiev don't win, both Porto and Chelsea progress.

KICKOFF: Here we go then! Chelsea get us underway going in search of just a point to guarantee their place in the last 16 of the Champions League.

There were some questions over how Porto would line up this evening, and it looks as though they have gone for three at the back, which will change to five when Chelsea have the ball. That is not a formation they have played under Lopetegui before, so it is certainly a risk from the visitors.

It's been an energetic start from Chelsea to this game, both on and off the ball. They are looking to get straight on the front foot when they do get possession, and working very hard to win it back when they lose it.

SAVE! Brahimi has his first threatening moment, almost wriggling through the middle before being forced out wide by a number of blue shirts. The ball eventually comes back out to him and he drills a cross/shot into the middle that Courtois palms away.

It looks as though Brahimi is operating in a wider role, with Corona the more central of the front three so far tonight, but that may well change as they match progresses. They have sprung something of a surprise on Mourinho with this formation.

It has been a good, fast-paced temp to this match so far. Chelsea are pressing in numbers and high up the field, limiting Porto's time on the ball, but so far the visitors have dealt with it.

Chelsea have the opening goal of the contest, and it is a controversial one! Hazard slid the ball through for Costa, who just about got the better of the last man to race clean through on goal. Casillas comes out to meet him and makes a big save, but the ball bounces back off Marcano and goes towards the net. Maicon hurls himself back to seemingly clear off the line, and the linesman's flag does not go up. However, the official behind the goal makes the decision that the ball did indeed cross the line, and the replays show that it was the correct decision.

The officials behind the goal have received plenty of criticisms since they were introduced, but that is exactly what they are there for. All too often they don't make big decisions, but that was a huge call and he got it spot on. It wasn't an easy one either as there wasn't much in it.

UPDATE: Dynamo Kiev have taken the lead against Maccabi Tel Aviv, so it is doubly bad news for Porto. As things stand, they are heading out of the Champions League.

PENALTY SHOUT! Big penalty shout for Chelsea as they go in search of a second! Oscar took the ball into the box before falling over the outstretched leg of Marcano. The referee is having none of it, though, and tells Oscar to get to his feet.

YELLOW CARD! Costa picks up a yellow card early here for a trip on Casillas after the Porto keeper had collected the ball and was looking to distribute it. Casillas made a meal of it, but Costa knew exactly what he was doing there. Some afters follow from the old Madrid rivals and international teammates, but nothing more comes of it.

Chelsea find themselves in a very strong position in this game now, but they are not resting on their laurels. They have looked full of energy and desire so far, certainly not like a side who have lost faith in their manager.

Brahimi looks to be Porto's best bet again tonight. He is yet to create anything really substantial, but he looks bright every time he gets the ball and Chelsea really need to keep a close eye on him for the entire 90 minutes.

Porto have actually had 63% possession in this match so far, but they are yet to create a big chance so far. The onus is entirely on them now, with two goals needed without reply as things stand.

CLOSE! Very nearly a second for Chelsea following so lovely link-up play from Oscar and Willian. The two Brazilians exchange passes on the edge of the box before the former tries to steer one in to the bottom corner. His effort takes a deflection to leave Casillas helpless, but luckily for the visitors it trickles just wide.

Ivanovic climbs highest from the resulting corner, but he is under pressure and can't get significant contact on his header.

YELLOW CARD! Matic joins Costa in the book for a trip that happened off the ball and the referee came back to. That means a suspension for Matic in the next match.

YELLOW CARD! Maxi Pereira also goes into the book for a bodycheck on Oscar.

That own goal was the fifth that Chelsea have benefited from this season, which makes it their second highest scorer this season behind Willian's six free kicks and above the likes of Costa and Hazard.

Chelsea have a good chance to swing the ball into the box as Maicon is penalised, giving Willian the chance over the dead ball. As usual, his delivery is a decent one, but this time Porto deal with it.

Brilliant footwork from Corona on the left flank as he dances past two challenges, only to then be stopped in his tracks by Ramires.

YELLOW CARD! Danilo goes into the book for barging Costa over, which means that he too will now miss the next match through suspension.

SAVE! Courtois is forced into action, but it is a routine save for the big Belgian. Brahimi turns and fires a shot away from 25 yards, but he doesn't really catch hold of it and Courtois is easily down to make the stop.

YELLOW CARD! Martins Indi is the fifth player to go into the book in this first half having swept away the legs of Costa. No complaints there.

SHOT! Another shooting chance for the hosts as Oscar slides the ball in for Costa, who is all alone and forced out wide. He still manages to get the low shot away, though, and it earns his team a corner as Casillas gets a fingertip to it.

So far, so good for Chelsea, then. They go into the break with a narrow lead over Porto that, as things stand, will see them progress into the last 16 of the Champions League as Group G winners. The performance has been good for the hosts too, although they did need a rather big stroke of luck to get the only goal of the game so far.

That goal arrived after just 12 minutes when Costa was sent clean through on goal, only to see his low effort saved by Iker Casillas. However, the ball bounced back against the backtracking Marcano and bobbled over the line despite Maicon's best efforts. The goal was initially not given by either the referee or the linesman, but the official behind the goal awarded it and the replays showed that he was right to do so.

Oscar came closest to a second goal for the hosts just before the half-hour mark when he played a one-two with Willian before looking to pass an effort into the corner from the edge of the box. The ball deflected off a defender to leave Casillas helpless, but the ball trickled the wrong side of the post from a Chelsea perspective.

There hasn't been to much to shout about in terms of clear chances aside from those two efforts, but it hasn't been a boring game by any means. Porto are yet to truly test Courtois, although the Belgian has been forced into a couple of saves that he would always expect to make. First he denied a cross/shot from Brahimi before also getting down to make a routine save from the same player shortly before half time.

It hasn't been Chelsea at their very best so far tonight, but their appetite and hunger has been clear to see both on and off the ball. Costa seems to have reacted well to being dropped, and those around him have been full of energy too. It certainly looks as though the players are still giving their all for Mourinho, and as things stand the Blues will be in the draw for the knockout rounds at the end of the evening.

For Porto, the message at half time simply has to be to attack. As mentioned, they haven't created a really good chance so far, and that needs to change in the coming 45 minutes. They need two goals without reply to progress and, in truth, it is hard to see where they are going to come from at the moment.

KICKOFF: Porto get us back underway for this second half with just 45 minutes to save their Champions League hopes for this season.

CHANCE! An early chance for Chelsea in this second half as Costa brings the ball forward, beating Marcano before slipping a pass out to Willian. The Brazilian's first touch takes him a little wide before he unleashes a stinging drive that Casillas parries away.

SAVE! Porto go straight up the other end and try a curling effort from range that looks destined for the top corner, but Courtois's size allows him to pluck it out of the air and make it look simple in the process.

Brahimi also tries his luck from outside the box for the visitors, but this time the ball flies well off target.

Surely that is Chelsea through to the knockout stages? The ball is thrown in to Costa, who holds it up well before laying it off to Hazard. Hazard in turn gives it out to Willian, who drives a powerful low strike past Casillas at the near post. That was a very crisp finish.

Porto now need to score three goals in the remaining 35 minutes to stay in the Champions League this season. It is a huge ask for them on the balance of how this match has gone, with Courtois still yet to be truly tested tonight.

The visitors look for a quick response as Layun sends a corner in towards the near post that Marcano nods wide.

PORTO SUBS: Here come the cavalry for Porto as Vincent Aboubakar and Ruben Neves replace Imbula and Pereira.

I doubt we have seen the last of the goals in this match. Porto will need to throw caution to the wind in this final half an hour, which should leave plenty of space open for Chelsea on the break.

Good chance for Porto to swing the ball into the box here as they win a free kick out wide to the left. A goal now could make things very interesting...

The delivery is a dangerous one, but Courtois gets enough on it and Chelsea immediately launch a counter. Hazard looks for Willian, but Casillas is quick off his line to mop up the danger.

CLOSE! Brilliant play from Corona down the right as he beats his man before delivering a fine cross into the middle. It reaches Brahimi at the back post and the Algerian curls one towards the far corner that flicks off Ivanovic and narrowly wide.

Porto are taking a gamble on every set piece at the moment, as they need to do. They are leaving just one player back, usually up against Hazard, which obviously leaves them susceptible to a quick counter. They have almost been caught in that manner twice already.

UPDATE: It looks as though both Chelsea and Arsenal will be joining Manchester City in the last 16 of the Champions League, with the Gunners leading Olympiacos 3-0 courtesy of a hat-trick from Olivier Giroud. It remains 1-0 to Dynamo Kiev over Maccabi, incidentally.

PENALTY SHOUT! Another penalty shout for Chelsea as Costa races through before being bundled over by Danilo. The referee deems it to be a fair shoulder barge, however, and waves the claims away.

PORTO SUB: A third and final change for Porto, and it is another attacking one as Cristian Tello replaces Herrera.

CHANCE! A chance for Chelsea to put this one to bed once and for all as Hazard and Willian combine to set Oscar up, but the Brazilian's cheeky back-heel is stopped by Casillas. Lovely football from Chelsea, but it was a fairly simple one for the keeper.

There are more goals in this one for Chelsea. Porto are all-out attack now and leaving space at the back, which Ivanovic looks to exploit with a swinging cross behind the backline that is just a yard too far in front of Hazard.

YELLOW CARD! At the other end Ivanovic is shown a yellow card for a heavy challenge from behind on Corona.

Fine defending from Terry to step in just in time to deny Aboubakar. Chelsea immediately race forward on another counter, but Costa leaves the ball when he knows that he is offside and the attack fizzles out.

This time it is Zouma who steps in with pace and power as the ball break to Corona in a good position, only for the young French defender to shrug the Porto man off the ball and win a free kick.

SAVE! Porto aren't giving this one up! Tello does really well to cut inside and fire a low strike that is skimming towards the bottom corner, but Courtois is at full stretch to tip it wide of the post.

CHANCE! Another chance on the break for the home side, with Costa the man to be released clean through on goal this time courtesy of Oscar ball over the top. Stamford Bridge waits in anticipation of the net bulging, but his first touch is poor and runs through to Casillas.

CHANCE! Big chance for Hazard this time as the cross arrives from the left which he nods into the arms of Casillas.

OFF THE POST! This could well be the night that Hazard breaks his duck for Chelsea this season, and he comes close here as he low strike from a tight angle hits the foot of the post before bouncing back off Casillas and out for a corner.

CHELSEA SUB: Chelsea's first change of the night sees Pedro replace Oscar.

It must be said that Chelsea have looked a little more like their old selves defensively tonight. Terry and Zouma have both been rocks at the back, and they all seem to gain so much confidence from having Courtois behind them too.

CHELSEA SUB: Another change for Chelsea as Mourinho looks to protect against the most unlikely of comebacks, bringing John Obi Mikel on for Costa, who has had a very good game tonight.

Jose Mourinho's name has echoed around Stamford Bridge on a few occasions tonight. This victory may well have saved his job, but the evidence both in the stands and on the pitch tonight has been that everyone at the club is still behind the manager.

CHELSEA SUB: A third and final change for Chelsea, and there will be no goal after all for Hazard. He comes off to be replaced by Loic Remy.

There will be three minutes of added time before Chelsea's place in the last 16 is officially confirmed. Meanwhile Remy has a chance moments after coming on, only to slice his effort well wide of the near post.

CLOSE! Almost a fine consolation for Brahimi late on as he cushions a volley narrowly past the far post.

Chelsea guarantee their place in the last 16 of the Champions League, then, and in the end it was all rather straightforward for Jose Mourinho's side. They need a huge stroke of luck for the opening goal when a Casillas save deflected off Marcano and over the line, despite the best efforts of Maicon, while Willian added a second seven minutes after the interval. Not only are they through, but they progress as group winners, which should hand them a favourable draw in the next round.

That is all we have time for this evening! Thank you very much for joining Sports Mole for what could well be a turning point in Chelsea's season as they book their place in the knockout stages of the Champions League. I will leave you with our match report, and be sure to stick around for reaction! We turn our attention to the Europa League tomorrow, so be sure to check back in for that too. From me, though, it is goodbye for now!