Manchester City defender Alex Greenwood has undergone knee surgery on a medial collateral ligament (MCL) injury.
The captain was stretchered off in the first half of Man City's Champions League win over St Polten earlier this month.
Manager Gareth Taylor had initially said the injury was “not as bad as first feared”, but a statement from the club on Thursday revealed Greenwood needed “her MCL repaired”.
Depending on the severity of the tear, MCL recovery can take anywhere from three to 12 months, with no timetable given for the defender's return to action.
Forwards Vivianne Miedema and Lauren Hemp are also sidelined with long-term knee injuries, while Khadija Shaw will not return until January.
Man City lost 3-0 to Barcelona in their last game before the winter break, surrendering top spot in their Champions League group, but had already qualified for the knockout stage.