Fletcher was ruled out for the rest of the season following the operation, which should resolve his ulcerative colitis.
Ferguson conceded that the Scot wasn't the same player as three or four years ago when he last returned, but hopes that this latest treatment will give him a chance to get back to his best.
"This improves his prospects. I felt he wasn't the Darren Fletcher of three or four years ago. When he comes back it will be in a different role," said Ferguson.
"The boy's attitude is absolutely brilliant."
United currently sit top of the Premier League table, seven points clear of rivals Manchester City.