One of football's worst-kept secrets was confirmed earlier this month when it was announced that the self-proclaimed 'Special One' Jose Mourinho had agreed a four-year contract to return to manage Chelsea.

That very afternoon, speculation was rife as to whom the 50-year-old would recruit to his playing staff in order to take the Premier League title back to Stamford Bridge for the first time since 2010.

Having trawled through the mountains of speculation, Sports Mole has whittled it down to five players that we feel will boost Chelsea's chance of being successful over the next few months - both domestically and abroad.

Eliaquim Mangala, Porto

By now, it's become clear that Mourinho likes his centre-back pairings to consist of one that is comfortable in possession of the ball, while the other is a lionheart who would throw himself in the way of anything - Ricardo Carvalho and John Terry from his first stint at Chelsea for example.

What he will find when the Blues return for pre-season training is Gary Cahill and Branislav Ivanovic (lionhearts) an ageing Terry and David Luiz, whose constant need to play with the ball on the edge of his own area borders on football suicide.

That is where the 6'2" figure of Mangala comes into play. The Frenchman has the physical presence to deal with the likes of Andy Carroll, but is also mobile enough to cope with the pace and movement of Sergio Aguero.

He is also happy to keep hold of the ball and can pick out a pass, almost making him Mourinho's desired defensive unit rolled into one player.

The 22-year-old has a release clause worth £30m and Porto at the moment appear to be reluctant to budge on that. Should the player indicate his wish to leave though, their demands may lower.

Luke Shaw, Southampton

Ashley Cole will not go on forever. In fact, there are signs that his powers may have started to wane ever so slightly over the last 12 months. England coach Roy Hodgson appears to believe that is the case, having sometimes picked Leighton Baines in the left-back role for the Three Lions of late.

While Ryan Bertrand is seen as Cole's cover, there are doubts over his ability defensively, with some believing him to be more effective further up the pitch.

He may only be 17 and not have signed a professional contract yet, but Southampton's Shaw looks to be the real deal. He has all the potential to go on and become a fine full-back, so who better to hone those skills with than Cole - arguably one of England's most consistent ever defenders?

There is a risk that should he join the Blues that his development may be stunted by sitting on the bench behind Cole, so perhaps another year with the Saints on loan wouldn't hurt.

What's more, he's a boyhood Chelsea fan, which would see him become an instant favourite of The Shed End at the Bridge.

Sami Khedira, Real Madrid

With the likes of Juan Mata, Oscar and Eden Hazard in the side, it's important that the Chelsea rearguard is given some protection. There will be times when Frank Lampard takes on the job, as well as Ramires.

There is also John Obi Mikel, but if reports are to be believed, Mourinho is prepared to part with the 26-year-old that the club fought so hard to sign in a battle with Manchester United back in 2006.

It seems as though that there were not many players that Mourinho didn't clash with at Madrid, but Khedira is one that appears to have remained loyal to his coach.

Knowing that he can trust the German international, Mourinho could make a move for him to plug the gap in front of his defence. The 26-year-old has also shown that he can pop up with a goal or two when it really matters.

Marco van Ginkel, Vitesse Arnhem

The Blues are currently jam-packed full of creative midfield players. As well as the three mentioned above, Marko Marin, Kevin de Bruyne, Victor Moses and Lucas Piazon are also on their books.

There are expected to be departures though, with both Marin and De Bruyne in particular heavily linked with moves to the Bundesliga.

Should that come to the fore, Mourinho will need to bring in at least one player to fill the void. Van Ginkel would be the ideal addition - being 20 he would not expect to play every week, but he possesses the potential to become a key member of the squad in the future.

He rose to prominence last season by scoring 12 goals in all competitions, which in turn earned him a call-up to the senior Netherlands squad.

Mario Gomez, Bayern Munich

With Fernando Torres and Demba Ba both tipped to move on before the start of the new campaign, that would leave Mourinho with a grand total of zero strikers!

A whole host of centre-forwards have been linked with a West London arrival, including Wayne Rooney and Edinson Cavani. The sticking point there would be that both of those like to come deep and collect the ball, which could lead to confusion among the front five.

Gomez is a proper goalscorer though - someone that comes alive inside the penalty area. Injuries and the form of Mario Mandzukic saw him struggle for matches last season, but he still scored 19 goals. The previous two campaigns were nothing short of clinical as he found the net an impressive 80 times in all competitions.

He's the sort of centre-forward that has no real interest on what is going on outside of the box, which would allow the likes of Mata and Hazard the time and space to be at their creative best.

The 27-year-old could also likely to be available for a reasonable price, especially if Bayern land Robert Lewandowksi.