More often than not this season, Frank Lampard has used a flat back-four, as part of either a 4-3-3 or 4-2-3-1 formation.
Fortunately for Lampard, he has four top-class central defenders with Antonio Rüdiger, Andreas Christensen, Fikayo Tomori and Kurt Zouma all at his disposal.
However, with all four now fully fit, this gives the Blues boss the ultimate dilemma; collected here are reasons behind why each would deserve a place in central defence at Villa Park this Sunday.
Following a groin injury which saw him side-lined from September to December earlier in the season, Rüdiger has gone on to play almost every minute of Premier League football since, making him a clear favourite of Lampard’s; the only exception to this being the Blues’ trip to AFC Bournemouth on 29 February.
Standing at 6 feet 2 inches, the German international is known for his commanding aerial presence, and this showed in an impressive performance earlier this year against Leicester City, where Rüdiger bagged himself a brace of headers in a 2-2 draw at the King Power Stadium.
Rüdiger’s goalscoring abilities set him apart from his competitors as he has more Premier League goals so far this season than Christensen, Tomori and Zouma combined, despite playing fewer games than all three.
Despite only making his first-team breakthrough in the last few seasons, Andreas Christensen has actually been at Chelsea since 2012, when he joined on a free transfer from Brondby.
Less powerful than Rüdiger, Christensen is far more well-known for his ability on the ball.
In the Premier League this season, the Danish international has a passing accuracy of 90%, which is not just higher than any other defender at Chelsea, but the joint highest at the club, alongside Mateo Kovacic and Billy Gilmour.
Christensen has also shown he is comfortable moving with the ball, he has a dribbling success rate of 100%. Therefore against a side like Aston Villa, who are likely to sit back and allow Chelsea possession, Christensen could be the perfect man to slot into the Blues backline.
Coming off the back of three consecutive loan spells at Hull City, Brighton & Hove Albion and Derby County, all at Championship level, huge questions were asked over whether Fikayo Tomori would be able to adapt to the Premier League.
However, Tomori silenced any doubters almost straight away, in just his second ever Premier League start, he scored a 30-yard screamer against Wolverhampton Wanderers in a 5-2 win at Molineux.
The shortest of the centre backs at Chelsea, Tomori is a far more agile defender who has adapted well at times when Lampard has opted for a three-man defence, showing glimpses of his youth team days where he often played at right back.
Despite still being one of the youngest players in the Chelsea squad at 22, Tomori’s value must not be underestimated, as he has the highest win rate out of his teammates in the same position, with the Blues winning 60% of their games when Tomori features.
With 22 Premier League appearances to his name already this season, Kurt Zouma has clearly benefitted from being able to keep fit throughout the current campaign.
It is also worth noting the fact, Zouma has been relied upon in some of Chelsea’s biggest games so far this season, with him starting every game away from home against the five members of the ‘top-six’ which Chelsea have played away.
Similarly, to Antonio Rüdiger, Zouma is known to use his physical power when defending, and despite only playing seven more times than Christensen and Tomori so far this season, Zouma has won more aerial battles than the pair combined.
His power combined with his surprising speed, helps to show exactly why Lampard has continued to put his faith in the French international.