Birmingham City midfielder Maikel Kieftenbeld will be out for six to nine months after damaging the anterior cruciate ligament in his right knee in their win against Leeds United.
The 28-year-old was stretchered off in the 57th minute of Saturday's win after a tackle with Kalvin Phillips.
The Dutchman has made 163 appearances since joining from Groningen in 2015.
Kieftenbeld's contract is set to expire in 2020, however Blues opted to trigger another year in light of the injury.
Saturday's win against promotion-chasing Leeds ended a run of five straight defeats for Birmingham City, with Che Adams' first-half goal helping them to victory.
Kieftenbeld has made 38 appearances in all competitions for Birmingham this season, scoring one goal.