Joe Hart admits Manchester City's grip on the Barclays Premier League title this season has been loosened by the Manchester United "killing machine".
Hart has seen the Red Devils open up a 15-point lead with just eight games remaining and concedes City have been "disappointing" in their defence of the title but he also gives credit to the way the Red Devils have swept aside all challengers to put them on the verge of another championship.
When asked why City have not been at their best, Hart said: "I don't know, I'd love to know. It would have been rectified."
He went on: "Maybe we have drawn more games than we would have liked to but it has not been a perfect season - and it needs to be pretty perfect to win this league.
"We have done well but we have been up against a killing machine that have kept turning out results no matter what.
"It is a tough league, it's hard to win games. Unfortunately when we do lose, United stretch that lead and it has been disappointing but we will keep going
"We worked so hard to get that title we are never going to just give it away. I'd imagine from the outside it looks that way, but that's just not the case."
Regarding City boss Roberto Mancini's criticism of some of his performances, Hart said: "You have got to be able to move on. Everyone is going to have their opinion.
"What is said in private, that's for behind the scenes but he (Mancini) is free to do his press conferences as he feels and if he feels you are not up to it ..."