Manchester City midfielder Kevin de Bruyne is likely to be out for around six weeks after injuring his right knee in Wednesday's League Cup semi-final win over Everton.
The Belgian international, 24, changed the game from the bench but fell awkwardly in injury time.
There were fears he could be out for the rest of the season.
"Kevin told me the only thing he can do is work hard and come back," his agent Patrick De Koster told Sky.
"Kevin is sad. His dream is to always be playing football. He will miss games like the League Cup final and in the Champions League, which are important."
Games Kevin de Bruyne is likely to miss
30 Jan: A v Aston Villa (FA Cup fourth round)
2 Feb: A v Sunderland
6 Feb: H v Leicester City
14 Feb: H v Tottenham Hotspur
20-21 Feb: FA Cup fifth round
24 Feb: A v Dynamo Kiev (Champions Lg last 16 1st leg)
28 Feb: v Liverpool (League Cup final, Wembley)
2 Mar: A v Liverpool
5 Mar: H v Aston Villa
City boss Pellegrini said on Wednesday he was "optimistic" that De Bruyne, the club's £55m club record signing, would not be out for the remainder of the campaign.
However, he is still expected to miss up to nine league and cup games, including the League Cup final with Liverpool at Wembley on 28 February.
"We'll see how important the damage is. It's not the cruciate ligament," said Pellegrini. "The doctor thinks, but he cannot be sure, that it's a problem in his medial ligament."
De Bruyne scored one goal and set up another to help City to a 4-3 aggregate victory over the Toffees.
Everton goalkeeper Joel Robles repeatedly tried to lift up De Bruyne as he lay injured and later apologised on social media.
"I would like to apologise to Kevin de Bruyne for my reaction to his injury," tweeted the 25-year-old Spaniard.
"In the heat of the moment I didn't realise he was badly hurt. I wish him all the best and a speedy recovery."