The effect selecting Thibaut Courtois ahead of Petr Cech may have had on Chelsea

Chelsea's defence has looked unusually shaky this season, and one thing that has changed has been the first choice goalkeeper.

It has been a pretty weird season for Chelsea, certainly from the outside looking in. They're a side that don't look as solid at the back, more fragile, more prone to errors and are leaking goals compared to last term.

Having said all that, they're firmly on course to record their fourth title win in the Premier League era, but it would be odd if Jose Mourinho were not a little concerned with what is happening with his side at the moment.

One massive change to his side has been the goalkeeper. Petr Cech was the solid, reliable servant at the back for the Blues for 10 seasons, but Mourinho took the decision to not let Thibaut Courtois extend his loan spell elsewhere - having helped Atletico Madrid to the La Liga title and reach the Champions League final - so the Belgian was back at Stamford Bridge and has been given the nod ahead of Cech.

It's a big change for a side that prides itself on defensive solidity. A different goalkeeper behind the defensive line can take some getting used to for the unit. This is not to say that either goalkeeper is better than the other. As Mourinho himself said, he has two of the best goalkeepers in the world at his disposal.

But why make the change and has it upset the balance at Stamford Bridge a little?

Comparison between Courtois this season and Cech this season and last in the Premier League and Champions League:

  PositionTeamSaves GAMEGood High Claim GAMEClean SheetError Lead To ShotAppearancesMins Played
Thibaut Courtois GK Chelsea 2.59 2.21 10 1 29 2,544
Petr Cech GK Chelsea 2.29 1.07 21 0 42 3,756

These suggest that Courtois has been much the busier than Cech in comparison to his deputy, while Cech seems to have a better ratio when it comes to keeping clean sheets [one in two compared to almost one in three for the Belgian].

Premier League 2013/14: 

  Saves GAMEGoals Conceded GAMEPossession PercentageError Lead To ShotOutfielder Block GAMETotal Tackle GAMEAppearances
Chelsea 2.53 0.71 55% 6 2.5 19.29 38

Premier League 2014/15:

  Saves GAMEGoals Conceded GAMEPossession PercentageError Lead To ShotOutfielder Block GAMETotal Tackle GAMEAppearances
Chelsea 2.34 0.86 56% 13 2.59 20.62 29

It just seems to be a simple face that Chelsea are under a lot more pressure this season, but there are a lot more errors leading to shots on goal this season than there were in the entirety of the last term - while the increase in the total tackles and outfielder blocks suggests there is probably a little more strain on the back line - all which contribute to a poorer defensive record and the goalkeeper being busier in the process.

Courtois seems to be more exposed when he is selected compared. It's hard to explain why Chelsea may have been 'un-Mourinho', the change to Courtois and a more errors among the defence may just be coincidence.

It may be because he's a younger and lesser experienced goalkeeper and the members of the back line are a little more disconcerted with a different goalkeeper behind them, or just that the defence isn't as strong this term and Mourinho may address it in the summer. But it all seems pretty odd, even though Chelsea are on course for a more successful season.

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