Manuel Pellegrini does not know when Vincent Kompany will be fit to return for Manchester City following his latest calf injury.
The City captain lasted just nine minutes against Sunderland on Boxing Day when he returned from his previous lay-off due to a calf problem.
Kompany suffered a grade two tear against the Black Cats and his current lay-off is his 12th for a calf injury since the start of the title-winning 2011-12 campaign and his third this season.
The Belgian has also missed matches because of hamstring and groin injuries in recent years and his latest set-back has raised questions whether his career could be in the balance.
Kompany was initially only expected to miss the first few weeks of the New Year but the Chilean manager hinted on Tuesday the central defender could be facing a lengthy spell out of action.
"It is difficult because Vincent is doing a lot of different things to try to understand and to find the reasons for so many injuries," said Pellegrini. "At this moment it is difficult to tell you an update about that."
Pellegrini later added: "Vincent maybe not so soon, but for the last part of the season he could be fit."
City's Premier League title challenge has suffered in Kompany's absence. Of the 11 games in which he has not featured, the team have kept just one clean sheet. When he has been on the field, they have only conceded once.
Now with Eliaquim Mangala also sidelined with a hamstring injury, City are looking short of central defensive options, but Pellegrini has no plans to sign cover during this month's transfer window.
He said: "We have (Martin) Demichelis, we have (Nicolas) Otamendi, we have Bacary Sagna, who can play in a central defensive position, we have Cameron (Humphreys), who is a young player who featured in pre-season with the squad.
"Mangala will return soon. So, at this moment, we are not thinking about making a change."