Hughes, Mancini's predecessor, returns to the Etihad Stadium with his new side on Sunday for a match that has major implications at the top and bottom of the Barclays Premier League.
Mancini said: "This is not important - on Sunday we play Manchester City against QPR.
"For me, they are a good team, they don't deserve to stay at the bottom.
"They want to do everything to stay in the Premier League and for this reason I think it will be a tough game.
"I don't know him very well but it is not Mancini against Hughes or Hughes against Mancini. It is City against QPR.
"One team plays for the title, the other plays for (to avoid) relegation."