Ahead of the title run in, Mancini labelled rivals Manchester United's remaining matches against Swansea City and Sunderland as "easy" in comparison to his side's game against Newcastle and QPR.
Black Cats boss Martin O'Neill has hit back at the Italian's suggestions, and now O'Shea has echoed his manager, pointing to his team's impressive showings against City this season, having drawn away and defeated them at home.
He told the Guardian: "Believe me, the two times City have played against us this season, they knew it wasn't an easy game. We've taken four points off them, and it should have been six if we think about the game at their place [a 3-3 draw in which Sunderland led 3-1].
"I think he (Mancini) is starting to enjoy his psychological games but, as the gaffer said, to call the integrity of the Premier League into question is disappointing. He's going for the title and he's going to try certain things. But he doesn't need to do that."
Former United player O'Shea also admitted to his surprise at the champions' collapse in the defence of their title, after they recently boasted an eight-point lead over City, who now lead the way on goal difference.
He said: "You would have expected, with all their experience, they would have managed to keep that advantage so close to the end of the season."