Chelsea: Caballero matches up to Courtois, but both lag their top-six peers

Willy Caballero preserved both of Chelsea’s last two clean-sheets, in the FA Cup quarter-finals against Hull and a month later in the semifinals against Southampton. He and Thibaut Courtois are equivalent in their respective competitions, but lag their peers among the top-six.

Willy Caballero has provided some of Chelsea’s more entertaingly nervy and audacious moments of the season in the domestic cup. He and Thibaut Courtois bring very different styles of play to the net, but with similar results. In fact, Chelsea’s primary and back-up keepers are more closely matched for their respective tasks than the other top-six goalkeeper batteries.

Caballero has started 12 games this season: 10 in the domestic cups and two in the Premier League. Of those 12, five have been clean sheets: 42%. Courtois has 42 starts – 40 in the Premier League and Champions League – with 16 clean sheets: 38%.

This 4% gap in clean-sheet percentage is the lowest among the primary-backup goalkeeper pairs in the top-six. At the other end is Liverpool’s pair of Loris Karius and Simon Mignolet. Karius’ clean-sheet percentage at 51% is 20 points higher than Mignolet’s. Interestingly, Karius and Mignolet have split their games most evenly this season. Whereas Courtois and Caballero differ by 30 games, Karius has played only five more than Mignolet.

The parity between Chelsea’s goalkeepers reflects itself in another way. Both Courtois and Caballero are fourth among their peers – primary or backup keeper – in clean-sheet percentage. Courtois trails Karius, David de Gea and Ederson. Caballero is behind Sergio Romero, David Ospina and Michel Vorm. The ranking improves only marginally for total number of clean sheets. Courtois moves ahead of Karius by two cleansheets, but Chelsea’s Belgian has played 15 more games.

These stats work out better for Caballero than Courtois. Chelsea signed the 36-year old on a free transfer to play domestic cup games and cover in case of injury and suspension. Caballero has fulfilled his assigned tasking to the same extent Chelsea’s primary goalkeeper has fulfilled his. The Argentinian even outlasted his predecessor by at least two rounds of the FA Cup.

But the equivalent stats do not imply an equal evaluation. Caballero came to Chelsea as a back-up, to be a back-up. This is not like the brief period when Petr Cech was Courtois’ back-up.

Courtois, on the other hand, is not just Chelsea’s primary goalkeeper. He is rated a world-class keeper, heir to Petr Cech if he can resist the urge to leave for Real Madrid. Like Eden Hazard, he is supposed to be better at his job than all but the best are at theirs. Instead, he lags behind truly world-class keepers like David de Gea, previous unheralded upstarts like Ederson and early-season banter-targets like Loris Karius. Instead of exceeding the standards of his peers, he meets the standards of his back-up.

A team’s defence obviously factors into the clean sheet percentage. Petr Cech is a victim of this, as he has the fewest among the six primary goalkeepers with 11 this season.

The influence of the defence is an interesting question, though, given the amount of variance among five of the goalkeeper batteries. Squad rotation among the outfield players for the domestic cups may play a role. Four of the six backup keepers have a higher clean sheet percentage than the primary keeper. This may reflect how wide the quality gap is between top-six Premier League clubs and the lower-tier opponents they tend to meet in the cups. Even with their backup keepers and a rotated squad they still heavily dominate these games.

Given the importance of defending, goalkeeping and clean sheets to a team’s success, it should be little surprise the Blues are fourth in clean sheet percentage and approaching fourth place in the Premier League table. Chelsea have little chance of improving their goalkeeping lot this summer, but should at least strengthen their defence. They can do this tactically, without any transfers, given the players they currently have.

Next: Antonio Conte still coming to terms with Jose Mourinho's legacy on transfers

Willy Caballero has become a surprisingly successful and worthwhile signing for Chelsea this season. Thibaut Courtois’ contract situation will be a major storyline of this summer, particularly if Belgium go deep into the World Cup. The Blues have few options to replace him, and his demands may be based on this scarcity rather than his output.