Two of European football's most famous and successful clubs meet in a monumental Champions League showdown on Wednesday night as Barcelona welcome Liverpool to Camp Nou for the first leg of their semi-final.

Both are five-time winners of the competition and are enjoying campaigns which could rank alongside any others in the illustrious histories of either club.

Barcelona

One down, two to go.

Barcelona's quest for a treble is now one-third complete after they secured an eighth La Liga title in 11 years at the weekend, and they can now turn their full attention to reaching the Champions League final for the first time since 2015.

Liverpool are the main obstacle standing in the way of Barcelona winning the treble for the third time in their history - after 2008-09 and 2014-15 - and Ernesto Valverde's side will not need to worry about their Copa del Rey final against Valencia until the final week of May.

La Blaugrana's three wins in the space of seven days ending on Saturday ensured that they can no longer be caught at the top of La Liga, crucially wrapping up the title before this mouth-watering double-header against Liverpool.

We can expect a much-changed side when they face Celta Vigo this weekend, then, but Valverde has already been protecting his most important players en route to clinching their domestic crown, with Lionel Messi in particular having been used relatively sparingly in the buildup to this first leg.

The Argentine maestro was needed to come off the bench and score the title-winning goal against Levante at the weekend, but the prospect of him being fresh and raring to go is surely Barcelona's biggest weapon in the formidable challenge that awaits them in this tie.

Messi's logic-defying tally of 46 goals in 45 games this season - not to mention his competition-leading 10 in the Champions League and 24 in 32 games against English opposition - make him the frontrunner for a sixth Ballon d'Or trophy this year, although the fate of this tie could be decided by how he fares against fellow contender Virgil van Dijk.

Messi remains the jewel in Barcelona's crown, of course, but as a team this crop have developed into masters of getting the job done - not always in the alluring style of some of their predecessors but just as effectively.

Indeed, despite not being at their best at various stages of the campaign, Barcelona have lost just four times across all competitions this season - twice in La Liga and twice in the Copa del Rey.

The Spanish giants are the only unbeaten side left in this season's Champions League, while they come into this match on a 22-game undefeated streak in any competition, stretching back to January.

Just one of those four defeats has come at Camp Nou too, where Valverde's side are 18 games unbeaten including eight wins on the bounce ahead of Liverpool's visit.

Wednesday will also mark six years to the day since Barcelona last lost a home game in the Champions League, winning 28 of their record-breaking 31 such matches in the meantime, although that last defeat did come in the semi-finals.

Barca have fallen at this hurdle to English opposition on three previous occasions, but their recent record against Premier League sides is impressive, losing just one of their last 15 such fixtures and already seeing off Tottenham Hotspur and Manchester United in this season's competition.

Liverpool are likely to pose a much bigger threat than either of their domestic rivals, though, and Barcelona will be aware that their only home defeats at the hands of English opposition were both inflicted by Wednesday's visitors.

Recent Champions League form: WDDWWW
Recent form (all competitions): WDWWWW

Liverpool

After a couple of Loris Karius clangers cost them in the final against Real Madrid last season, Liverpool now find themselves within touching distance of having the chance to redeem themselves in the Spanish capital itself.

The class of 2018-19 looks even more capable of clinching that sixth European Cup - thanks largely to Alisson Becker now tending the goal - but if they are to truly prove their credentials then they must first get past the might of Barcelona.

There is no doubt that Liverpool have re-established themselves at the top table of European football; even without back-to-back Champions League semi-final appearances, a tally of 91 points and counting in the Premier League is proof that they are back amongst the elite.

Yet it still may not be enough to win the title with matters out of their hands, and two more wins for Manchester City would see Liverpool garner the highest-ever points tally without being crowned English champions, having done the same in the goalscoring stakes during their last title tilt in 2013-14.

Luis Suarez, now of Barcelona, was their talisman during that campaign, but this time around they have had numerous players step up to the plate - from PFA Players' Player of the Year Van Dijk to full-backs Andrew Robertson and Trent Alexander-Arnold to Golden Boot-chasing duo Sadio Mane and Mohamed Salah.

The Champions League may well be their best chance of a first trophy under Klopp this season, though, and Liverpool will certainly arrive at Camp Nou full of confidence having won their last 10 matches across all competitions - most recently a 5-0 drubbing of Huddersfield Town on Friday night.

The visitors' unbeaten streak stretches back even further to 19 matches - including 14 wins - with their last defeat coming in January, as is the case with their hosts too.

One cause for concern could be the Reds' away record in this season's competition having lost to Napoli, Red Star Belgrade and Paris Saint-Germain on their travels in the group stages, but Klopp appears to have fixed that problem with confident wins away to Bayern Munich and Porto so far in the knockout rounds.

Indeed, across all competitions Liverpool are unbeaten in nine away games and have won their last five in a row - they have not won six on the bounce since May 2006.

Ultimately a win is not the be-all and end-all for Liverpool on Wednesday night, though, and they will be confident of at least getting an away goal to take back to Anfield next week.

Klopp's side still thrive when afforded space to attack at pace, and with Barcelona unlikely to alter their own approach for anyone, there could be plenty of opportunities for that at Camp Nou.

Liverpool are bound to take particular encouragement from Barca's recent 4-4 draw against Villarreal, when they were continually ripped apart at the back by sheer pace.

Recent Champions League form: LWDWWW
Recent form (all competitions): WWWWWW

Team News

Liverpool are sweating over the fitness of Roberto Firmino, who missed the win over Huddersfield on Friday night due to a small groin tear - although Klopp played down the severity of the problem and the Brazilian could recover in time for Wednesday.

Fabinho was also absent last time out after suffering a blow to the head during a very brief substitute appearance against Cardiff City, but that was a precaution and he is expected to be available.

Adam Lallana is the only other injury doubt for the visitors, but Klopp has decisions to make elsewhere with Joe Gomez, Joel Matip and James Milner among the players pushing for recalls.

Barcelona will welcome their talisman Messi back into the starting lineup after he was only a half-time introduction at the weekend, when Sergio Busquets was also rested.

Suarez, who scored 69 goals in 11 league games for Liverpool, will lead the line for the hosts, but the position of another former Merseyside favourite is less certain with Philippe Coutinho competing for a place with Ousmane Dembele.

Valverde must also decide whether to start the combative Arturo Vidal or more creative Ivan Rakitic, while Sergi Roberto could come in for Nelson Semedo at right-back.

Rafinha, who has been sidelined since November with a knee ligament injury, is the only guaranteed absentee for Barcelona.

Barcelona possible starting lineup:
Ter Stegen; Roberto, Pique, Lenglet, Alba; Rakitic, Busquets, Arthur; Messi, Suarez, Dembele

Liverpool possible starting lineup:
Alisson; Alexander-Arnold, Matip, Van Dijk, Robertson; Henderson, Fabinho, Wijnaldum; Salah, Firmino, Mane

Head To Head

This will be the first meeting of these two European giants since the first knockout round of the 2006-07 competition, when Liverpool progressed on away goals courtesy of a 2-1 win at Camp Nou.

Indeed, Liverpool are unbeaten on four previous visits to the home of Barcelona, winning two and drawing two. Overall, the Reds edge the head-to-head record with three wins to Barca's two, and three draws.

The English outfit have won all three previous two-legged ties between these two teams, though, going on to lift the UEFA Cup in 1975-76 and again in 2000-01 after beating Barcelona on the way.

We say: Barcelona 2-2 Liverpool

This is such a difficult match to call. It is hard to back against Barcelona at any stage when they have Messi in their ranks, but Liverpool match up well against their Spanish counterparts and seem to be strong in areas that Barca tend to struggle with - most notably attacking pace. It should be an entertaining contest whatever happens, and we cannot split the two teams.