The Chelsea starlet suffered the knock in training last week after going over on his ankle in a session on Thursday.
After going for a scan the next day, early indications are that Lavia has suffered ligament damage, meaning that he could be ruled out until November, according to the Mail.
While yet to be confirmed, the news would be a huge blow to Chelsea who are desperate to see their new signing in action.
The Blues signed Lavia from Southampton in a deal worth £58million over the summer.
With such a significant outlay for the 19-year-old, fans are desperate to see the starlet in action, but that wait now looks set to continue.
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Chelsea return to Premier League action on Sunday as they travel to face Bournemouth at the Vitality Stadium.
They'll then face Aston Villa, Fulham and Burnley in the Premier League and Brighton in the Carabao Cup before the next international break in October.
With Arsenal and Brentford lined up after the October break, Lavia will be hoping that he can back in contention for those games in order to kickstart his Chelsea career going into November.