Manchester City midfielder Kevin De Bruyne has suffered suspected knee ligament damage following Manchester City's 4-3 aggregate win over Everton in the Capital One Cup on Wednesday.
The Belgium international was injured in the closing stages City's victory at the Etihad Stadium and had to be stretchered off.
The 3-1 score on the night secured a Wembley final date against Liverpool on February 28, but City now face a nervous wait to find out the extent of the injury to one of their most influential players.
De Bruyne, who scored one goal and made another on Wednesday night, suffered the injury following an innocuous looking challenge from Everton defender Ramiro Funes Mori.
"It's difficult to tell with De Bruyne's injury. It could be the medial ligament but we will know more tomorrow (Thursday)," Manchester City manager Manuel Pellegrini told Sky Sports 1 HD.
"He has been very important to us all season."
Asked if De Bruyne would miss the rest of the season, Pellegrini added: "I hope not. It is very difficult to know in this moment but I am optimistic he will not be out for the rest of the season."
After the game, Everton goalkeeper Joel Robles apologised to De Bruyne for attempting to pick him up after he went down injured.
Robles tweeted: "I would like to apologise to Kevin De Bruyne for my reaction to his injury. In the heat of the moment I didn't realise he was badly hurt.
"I wish him all the best and a speedy recovery."