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 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."
Meanwhile, Hughes's advisor Kia Joorabchian has refuted claims the Welshman will receive a £1 million bonus for keeping QPR in the Premier League.
With so much at stake, several newspapers have reported Hughes will receive a hefty pay day should QPR retain their top-flight status.
Joorabchian, though, claims Hughes, who took over as R's manager in January after Neil Warnock was sacked, is at the London club for the long haul.
"He knew he was taking the job in the middle of the season, quite late on in January," Joorabchian told Sky Sports News. "The directive of the owners and the chief executive there was that they wanted to build the club from the base up and they were looking for the right man to do it.
"If it meant it would take a few years to build it then that's how it was and that was the whole thing of signing (Hughes) in that there was no bonus at all for him or his team for staying up."