Mancini conceded several weeks ago that the destination of the trophy appeared to be the red side of Manchester and a 3-1 defeat for the current title holders at Tottenham could see United crowned champions sooner rather than later.
Spurs' win, courtesy of goals from Clint Dempsey, Jermain Defoe and Gareth Bale, reignites their own quest for a top-four finish and means United can seal their 20th league title with victory over Aston Villa on Monday night.
Mancini admits the Red Devils are deserving champions, even if he does not believe they have the better team.
"It (the title race) was finished three or four weeks ago," Mancini added.
"They are not a better team but they deserve to win this title because we lost a lot of points in games we probably didn't deserve to lose.
"But United won a lot of games in a row with goals and deserve to win the title."
An early Samir Nasri goal had set City on their way to dragging their seemingly forlorn title challenge on for another week but three goals in a scintillating seven-minute spell for Spurs left Mancini eying his side's defending.
"We did two big mistakes," Mancini said.
"It's not easy to play here against Tottenham. They are a really good team with good players and a good manager. To come here and played like we did is not easy.
"We played well, we gave a good performance for almost 80 minutes and we had a chance to score the second goal. But we didn't score and after that we did two big mistakes.
"We had the game under control. Tottenham were trying to win because it was important for them, but I think we lost the game through our own fault."