Hughes, who was sacked prior to Mancini's arrival at the Etihad Stadium in December 2009, takes his current side to Eastlands on Sunday needing points to be sure of avoiding relegation.
Depriving City of victory could also deny them the Barclays Premier League title but while some have suggested that might give Hughes double reason for motivation, Mancini claims the teams are all that matter.
The Italian 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 [Hughes] 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 [to avoid] relegation."
City lead the table on goal difference from Manchester United heading into the final fixture and so only need to match their rivals' result to claim a first title in 44 years.
Mancini accepts there may be nerves in the final hours before the game but says there has been no tension in training this week.
He said: "It is a normal week, without problem, without injury. We have worked well. The players are very well. I think maybe tomorrow, Saturday, we can have pressure - I don't know - because it is the last game, but it doesn't change our situation.
"We need to play another difficult game. We need only to have focus about the game."