Chelsea have confirmed that centre-back Wesley Fofana has undergone surgery after rupturing his anterior cruciate ligament.
The French defender did not travel with Chelsea to the United States for their pre-season tour after being diagnosed with an injury which the Blues have now confirmed is significantly worse than first feared.
"Defender Wesley Fofana has undergone anterior cruciate ligament reconstruction surgery," a statement read.
"The 22-year-old did not travel to America for the club's pre-season tour due to specialist medical assessments, which unfortunately confirmed that an operation would be required.
"Wesley will now begin his recovery and work with the club's medical department at Cobham during his rehabilitation phase."
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Centre-back remains a position of uncertainty for Chelsea, who are considering their options following Fofana's injury.
Academy graduate Levi Colwill remains a top target for a number of Premier League sides - Brighton and Liverpool are keen to get a deal done - but Chelsea have long insisted the 20-year-old is not for sale, even before Fofana's injury.
Colwill is expected to remain at Chelsea alongside Benoit Badiashile, who also did not travel for pre-season through injury, and 38-year-old Thiago Silva. Trevoh Chalobah is also on the books but has attracted plenty of interest from elsewhere.
New manager Mauricio Pochettino took 20-year-old Bashir Humphreys and 19-year-old Alfie Gilchrist to the US to help cover the senior absences.
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This article was originally published on 90min as Wesley Fofana undergoes surgery after ACL injury.