The Scotland midfielder has missed much of this season with a serious bowel condition.
"We're hoping he'll start pre-season training," said manager Sir Alex Ferguson. "He's on the recovery road at the moment and is doing some work.
"We can't assess it [yet] because we don't know enough about it, but Darren's medical people are dealing with that and our doctor has a good idea of the situation.
"At the moment the boy is doing his best to come back."