In the space of several weeks, Chelsea's defensive options have suddenly looked pretty thin. Wesley Fofana and Kalidou Koulibaly have both gone down injured, with the latter hopefully absent no longer than Tuesday evening's clash with Red Bull Salzburg after missing the Manchester United game.
Reece James' knee injury has also made Graham Potter's task of forming a more consistent Chelsea team a trickier task, whilst N'Golo Kante's hamstring surgery only heightens the importance of new midfield additions in the upcoming transfer window.
Potter has mainly stuck with a three-at-the-back system since replacing Thomas Tuchel. There have been two notable exceptions in the wins over Crystal Palace and Wolves, where the Blues played a 4-2-2-2 and 4-2-3-1. But even in the Wolves game, Marc Cucurella would naturally slot into a left centre-back role when required.
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With Koulibaly unavailable on Saturday and Chelsea's midfield being easily overrun by a confident Manchester United, Potter altered his shape, replacing Cucurella with Mateo Kovacic and moving to a 4-3-3.
The change was more a tactical necessity in a game where Chelsea had no control than altering purely based on injury problems. The addition of an extra body in midfield quickly made a difference, soon the numerical superiority United were enjoying in the centre of the park faded and there was a method for Chelsea to play out of their opponent's press.
It is in the short and long-term across the next weeks where we may see this formation remain based on the lack of sufficient options if injury concerns persist for Potter.
With no Koulibaly or Fofana, sticking with a back-three forces him to either shift Cucurella or Cesar Azpilicueta into that trio. Cucurella has not looked sharp in recent weeks, likely impacted by a recent illness as explained by Potter in Monday's press conference. Whilst Azpilicueta at 33 is not the inspiring choice many would have hoped Chelsea would still be relying upon after an expensive summer rebuild.
The two questions that also spring up should Potter shift more permanently to a back-four is the use of Thiago Silva and attacking personnel.
Silva's minutes, as we have focused on before, need to be managed wisely despite his undeniable importance to the team. And the issue with a growing injury list likely increases the strain on a player already facing higher demands in a congested schedule. Potter may be forced to play Silva more than he likes in the weeks before the World Cup.
In attack, the questions are more interesting and potentially exciting. Under Tuchel there was a critique of how attackers were struggling and reportedly feeling unhappy, adding an extra body in central midfield opens up the potential for players to operate in roles that better suit their skillset.
The familiarity the current squad have with the three-back system is clear and not silly to lean on. However, with Potter not being scared to alter his set-up depending on the situation, there could be an evolution sooner than anticipated.
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