For the third successive home game, Thomas Tuchel walked into the small media room at Stamford Bridge and delivered a post-match press conference full of frustration, irritation and exasperation. The Chelsea head coach made no attempt to hide his emotions.
"We thought we learned our lesson from Brentford and Real Madrid, but obviously not," Tuchel said after his side's 4-2 defeat to Arsenal. "The players have to face the reality that it's impossible to win matches if you make this amount of mistakes – and mistakes of this calibre. It's simply impossible. I haven't seen it in any other matches, but I see it now in consecutive matches of our games, and it has to stop."
Chelsea will have an opportunity to put things right on Sunday against West Ham United. It's another London derby against a side pushing hard for a top-four finish in the Premier League. The Blues will not have it easy as they attempt to end a disappointing run of results at Stamford Bridge.
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Tuchel will not be able to call upon his most influential midfielder, either. Mateo Kovacic suffered an ankle injury in the FA Cup semi-final win over Crystal Palace on Sunday, and the Chelsea head coach was downbeat on the Croatian's chances of featuring in the imminent future.
"It's a ligament injury," Tuchel explained ahead of the defeat to Arsenal. "Hopefully, [he will] not be longer than two weeks out, but this is a long time for us in terms of games. Hopefully, as short as possible."
At the start of the campaign, an injury to Kovacic wouldn't have caused huge alarm. Chelsea had Jorginho and N'Golo Kante in the form of their careers, while Ruben Loftus-Cheek and Saul Niguez, signed on loan from Atletico Madrid, were on hand to step in if required. It's a very different situation now.
Jorginho and Kante have struggled for form since the turn of the year, and while there have been impressive outings from Loftus-Cheek, the academy graduate hasn't been able to show his best on a consistent basis in midfield. Saul, meanwhile, hasn't featured for more than a month and hasn't threatened to break into the starting XI with any regularity.
Kovacic's importance to Tuchel's side has been highlighted in Chelsea's previous three home outings, all of which have ended in defeat. In the 4-1 defeat to Brentford, the Croatian was introduced from the bench only after the Blues had conceded three times in ten minutes. The game was effectively over.
Four days later – and very unexpectedly – Kovacic was again among the substitutes for the visit of Real Madrid, who in the opening period managed to score twice and lead 2-1 at the interval. The midfielder was summoned at half-time, and while Chelsea were far better in the second half, a mistake from Edouard Mendy meant Los Blancos claimed a 3-1 victory that, despite the best efforts of Tuchel's side, couldn't be overturned in the second leg.
Then came Arsenal, and with Kovacic out of action, Tuchel selected a midfield trio of Loftus-Cheek, Kante and Mason Mount. Once more, Chelsea were far too easy to play through, and their backline was ruthlessly exposed. The Gunners scored four goals, and in truth, it could have been more.
"It's not about individual players," Tuchel insisted in the aftermath of the Arsenal defeat. "A defensive performance is a team performance, and an offensive performance is a team performance." Yet there is no denying that at the present time, Chelsea are a far more structured and effective team when Kovacic starts in the midfield.
A quick dive into Kovacic's underlying numbers showcases why. Per FBREF, no Chelsea midfielder betters his 2.45 tackles per 90 this term, while he is averaging more successful pressures per 90 (7.03) than Kante, Jorginho, Loftus-Cheek and Saul. And on the ball, he is having a similar impact.
The 27-year-old is playing 1.42 key passes per 90 – most of the aforementioned midfielders – and 6.65 passes per 90 into the final third of the pitch. It's partly why Kovacic's expected goals assisted per 90 has jumped to 0.24, which is the highest figure of his Chelsea career by some distance.
This has been the campaign in which everything has come together for Kovacic. He has proved himself one of Europe's finest midfielders and certainly Chelsea's most important. It's why Tuchel – and Blues supporters – will be desperate to have the Croatian back fit and available for the season run-in.
