Van Persie hurt his hip after colliding with a camera in the build-up to United's first goal and he was eventually replaced six minutes before half-time by Danny Welbeck.
The Premier League's top scorer will be assessed in the next few days, but Ferguson expects the Dutchman to be available for the second leg of the UEFA Champions League tie against Real on 5 March.
"He collided into a camera which was dug out of a piece of ground, he collided into the base of it and that's given him a sore hip," Ferguson told Sky Sports.
"I imagine it will be tender and sore for a few days, but hopefully he'll be alright, particularly for the Real game."
The victory at Loftus Road was secured by a stunning goal from Rafael and a late finish from the evergreen Ryan Giggs, and opened up a 15-point gap to reigning champions Manchester City.
Ferguson added: "We're in a better position today than we were yesterday. It's one game less and it's really important that the only way we approach it is by winning the next game and then try winning the next game.
"It was a lively pitch, a tight ground and it was a game more about determination and concentration, particularly the defending part, which we did very well.
"It was a little scrappy at times, but we got a fantastic goal to set us up to make us hard to beat. It was a great strike from Rafael and he has made a great contribution this season."