Former Blues forward Alan Judge, now with Colchester United, is facing up to a year out of the game having suffered a triple rupture in his left knee.
The 34-year-old suffered the injury during Saturday’s 1-0 League Two defeat at Sutton United.
"Unfortunately, Judgy has suffered a bad one,” physio Hayden Clifton told the U’s official website.
"The injury is a triple rupture in his left knee with the ACL (anterior cruciate ligament), PCL (posterior cruciate ligament) and MCL (medial collateral ligament) all affected.
"It looked a serious one straightaway and we're looking at it being around a year to a full return to playing for Alan.”
Former Republic of Ireland international Judge previously had 20 months on the sidelines after suffering a double compound fracture to his leg in an April 2016 game against the Blues at Portman Road while playing for Brentford.
Judge was released by Town in the summer of 2021 after two and a half years at the club and subsequently was one of a number of former Blues to join the U's.