Hull City defender Moses Odubajo may miss the whole season after sustaining his second serious knee injury in just over three months.
The 23-year-old will have surgery next week after fracturing a kneecap during a non-contact training session.
The club said Odubajo had been making "excellent strides" after dislocating the same kneecap in July.
It added the ligaments he had reconstructed then "remain intact" and he would be out for about six months.
Hull signed Odubajo for £3.5m in July 2015 and he made 45 appearances in the Championship as they won promotion to the Premier League via the play-offs.