Chelsea defender Wesley Fofana has undergone anterior cruciate ligament surgery which is set to rule him out of action for several months.
The 22-year-old did not travel with the Blues squad on a pre-season tour to the United States in order to have “specialist medical assessments”.
The London club said the tests on Fofana’s knee “unfortunately confirmed that an operation would be required”.
The France centre-back joined Chelsea from Leicester for £70m last summer.
“Wesley will now begin his recovery and work with the club’s medical department at Cobham during his rehabilitation phase,” added a Chelsea statement.
It is another injury setback for Fofana, who broke his leg while at Leicester in August 2021 before returning to action the following March.
He was then sidelined for more than four months last season with a knee injury picked up playing against AC Milan in the Champions League.
Having played twice for Leicester last season, the central defender made 15 appearances for Chelsea and five in the Champions League.
Fofana’s absence comes following a summer in which defenders Kalidou Koulibaly and Cesar Azpilicueta left the club.
Defenders Benoit Badiashile and Reece James have also not travelled to the US, with Thiago Silva, Trevoh Chalobah, Levi Colwill, Alfie Gilchrist and Bashir Humphreys the main centre-back options available to manager Mauricio Pochettino.