The Belgian, having recently returned from long-term injury, was forced off on eight minutes in their Champions League draw at Qarabag.
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Speaking after the 2-2 result, Maresca said: "Yeah, we feel very sorry especially for him because he's not able to be fit for a long, long period.
"We will see now as it's too early to understand what kind of injury. Hopefully it's not a big injury.
"I think it's a quad injury."
Lavia has been plagued by injury since joining Chelsea from Southampton in 2023.