Pep Guardiola stopped short of ruling Ilkay Gundogan out for the rest of the season as it was confirmed the midfielder had suffered a cruciate knee ligament injury.
Gundogan sustained the injury in Manchester City's Premier League victory over Watford on Wednesday, with reports suggesting his 2016-17 campaign was over.
The Germany international suffered the setback when he was fouled by Nordin Amrabat in the 34th minute of the 2-0 win and was eventually replaced by Fernando one minute before half-time after attempting to play on.
Guardiola is reluctant to put a timeframe on the 26-year-old's return, but did confirm the need for surgery.
He said: "He will be out for a [long] time, but precisely what he has... I think the doctors are the right people to tell what he has. It is so so difficult for him, we are sad for him.
"We are going to miss him a lot but it is what it is. He is unlucky, sometimes these things happen in football.
"Now we need him to feel we are there and wait and come back safe. He's going to be operated [on] and be back as soon as possible."
Gundogan has a long history with injuries - a back problem saw him miss the 2013-14 season for Borussia Dortmund along with the World Cup, while a knee problem ruled him out of Euro 2016.