The 28-year-old joined the relegation-threatened Rs on the final day of the January transfer window in a £12.5 million move from Russian outfit Anzhi.
Samba has played two games for the club since his arrival, a 0-0 draw with Norwich City on his debut followed by a 4-1 loss to Swansea City - but the centre-back is not fazed by the prospect of meeting the Premier League's top goalscorer Van Persie.
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"Van Persie is an excellent player but I’ve been working on my fitness and I’m really much fitter than I was for the last game at Swansea, so it will be more difficult to beat me," Samba is quoted as saying by The Sun.
"He is on fire but I am positive I can have a good game against him - although it is not only him we have to stop because United have a lot of top players.
“They will win the Premier League this year but they are coming to QPR and we need the points more.
"When you play against top teams, you need to be on top of your game. We have everyone pointing in the same direction and we need to put that into practice out on the pitch."
QPR are currently four points adrift at the bottom of the Premier League table, with just two wins from 26 games.
Samba left Blackburn 12 months ago when the Lancashire side were in the midst of a relegation battle, and while then-manager Steve Kean was unable to stop the club dropping into the Championship, the defender insists he can utilise his experience of similar situations to help the Rs.
He said: "I’ve been bought for a reason — because QPR believe I can make a difference.
"I certainly believed I could lead the team. I don’t know if it will be enough but, one thing is for sure, I will do my best to help the team.
"I don’t think here is really similar to what happened at Blackburn. Emotionally, it’s very different, too. But, of course, when you get some experience you know how to handle it better. And that’s something I can help with.
"When you know what’s going on, sometimes you see how a player can react and you can say, 'Guys, just keep calm and let’s talk about what’s gone wrong'."