Sir Alex Ferguson is hoping Darren Fletcher can make a full recovery, but is not putting a timescale on the Manchester United midfielder's return to action.
The Premier League champions revealed earlier this week that Fletcher is to take an extended break from football as he is suffering from a chronic inflammatory bowel condition.
The Scotland captain missed two months towards the end of last season due to the illness and also sat out United's pre-season tour to North America to work on his fitness.
He returned to action for his national team in September's Euro 2012 qualifiers and has gone on to make 10 appearances for the Red Devils this season.
Ferguson believes the right decision has been made to give Fletcher time to recover and acknowledged his absence will be a loss for United.
"The medical people have made the right decision," said Ferguson. "They regarded Darren's health as the more important issue and we as a club agree with that.
"He's not been in training - he's been in hospital for a few days. He'll rest now.
"He's a loss - he's such a great professional and it's not easy to replace that, but we'll think about that. Hopefully he'll make a full recovery.
"It's obviously going to take a bit of time and rest is the most important thing at the moment. I can't put a timescale on it."