Giggs claims it could still be a successful campaign if they go far in the FA Cup and Champions League.
“I think United would take second now and have to concentrate on keeping hold of that," Giggs told Sky Sports.
“You have to hold up your hands and say City have been the best team, so second place and good runs in the FA Cup and Champions League would represent a good campaign.
“I think they'd have to win every game between now and the end of the season, which is virtually impossible, and expect City to lose quite a few games, which also looks pretty unlikely.
“It is just those little mistakes. They should have beaten Leicester by three or four and then you get a knock-on with the Burnley game, where they were really poor in the first half.
“And then the Southampton shut-out, so they need to focus on those issues before thinking about challenging City."