Antonio Conte has insisted that the first-half injury sustained by Willian acted as the turning point in Chelsea's defeat to Arsenal.
The Blues exited the EFL Cup at the semi-final stage on Wednesday evening, going down 2-1 at the Emirates Stadium after letting an early lead slip through their grasp.
Chelsea were deservedly in front seven minutes in through a well-worked Eden Hazard goal, but Arsenal soon hit back and would go on to book their place in next month's final.
Conte believes that losing Willian to a minor hamstring problem on the half-hour mark was a key moment in the match, as new signing Ross Barkley was brought on in his place and Chelsea's shape shifted.
"I think that Willian injury was decisive because we don't have many players to make substitutions," he told reporters after the match. "[Alvaro] Morata was out and today after the injury to Willian, I was a bit forced to decide to play with Ross Barkley.
"He is a really good player and has a good prospect and is very important for Chelsea, but at the same time he needs a bit of time to understand our idea of football. He has to work a lot but I am very happy for his game and for his effort.
"I spoke with [Willian] and he said he felt a bit of a problem in his hamstring, but he doesn't think it is serious. I hope that this feeling, sensation is right."
Chelsea return to action on Sunday lunchtime with a home match against Newcastle United in the fourth round of the FA Cup.
