Chelsea head coach Maurizio Sarri criticised his players' attitude and felt they were overconfident after a shock 2-1 loss to Wolves on Wednesday.
Ruben Loftus-Cheek's opener had Chelsea on track at the Molineux, only for second-half goals from Raul Jimenez and Diogo Jota to see the hosts claim a surprise Premier League win.
The result saw Sarri's side slide to fourth in the table, 10 points behind champions Manchester City ahead of their clash with the league leaders on Saturday.
Sarri feels the defeat to Wolves may help Chelsea as he praised Pep Guardiola's high-flying City.
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"As I said before, City are the best in Europe, maybe in the world, they can win or not the Champions League, but that depends on the moments," he told a news conference.
"Last season I think City were the best team in the Champions League, but then for two matches they played maybe not in the best moment of the City.
"If you have to play against them for 10 months they are the best in the world, I think, at the moment. So the match is difficult for this reason.
"Of course, after this match we lost confidence, but maybe it is better. Sometimes my players show me that they have too much confidence."
Sarri made five changes to the team that beat Fulham on Sunday, with Jorginho and David Luiz among the unused substitutes.
Asked about his selection, the Italian played down the impact of the changes, saying he was unhappy with the way his side suffered defeat.
"If you had asked me the same question after 55 minutes I would say yes, I was really very happy [with the selection]," he said.
"We lost everything, our football, the result, everything for an accident, a goal. It can happen, but I don't think it depends on the changes.
"It depends on the mentality of the team, I think. It was without reaction, we can lose a match, but not without a reaction."