The 29-year-old arrived from Bayern Munich with such high expectations three years ago.
Unfortunately, he also landed at Old Trafford with a chronic tendinitis problem that after a stellar 2008, which saw Hargreaves win both the Premier League and Champions League, required surgery on his knees that kept him out for over 19 months.
A further setback followed this summer and then, when Hargreaves did make a surprise return against Wolverhampton Wanderers in November, the £18m star lasted barely five minutes before tearing his hamstring. Now Hargreaves has gone to Germany for what Ferguson describes as "therapeutic" treatment and the Scot's concern is obvious.
"He has not played for over two years so we would have to be super-optimistic to think everything in the garden was rosy about him making comebacks," he said.
"What we are trying to do is help the lad. That in itself is our biggest challenge. We want to help the lad try to get back to a level where he can still play football."

Ferguson insists Hargreaves was ready to make his comeback when he was thrown into the fray at Old Trafford a month ago, even though he had no warm-up matches as build-up.
The midfielder signalled there was a problem within a couple of minutes of kick-off, and though he did try to battle through the pain, he found it was impossible.
"This hamstring injury is a real kick in the teeth," said Ferguson.
"He was doing so well in training before the Wolves game. He was absolutely superb.
"There were no qualms whatsoever about putting him in, even though he had only trained for nine days.
"We were confident enough to play him but unfortunately it has proved to be a disappointment for us.
"If he had realised early enough and come off before he had done any more damage, it could have been three to four weeks. But it is a complete tear.
"He has to fight it. There is no other way."