As reported by The Times (subscription required), the Dutch striker has been playing through the pain with pregame injections. This report also painted a picture of annoyance, insinuating that he has demanded talks with David Moyes about jeapordising his career.
If that was still bothering him, he didn't show it.
Instead, he produced a masterful display against Martin Jol's side, playing a part in all three goals and generally causing problems for Fulham.
In under 15 minutes, he showed just why he is so valuable to his manager, club and city.
First, it was through production as a pinpoint through ball split the Cottagers defence and found Wayne Rooney. Rooney squared the ball to Antonio Valencia to open the scoring in the ninth minute.
Before Fulham had time to properly regroup, Van Persie had found them out again.
This time it was Adnan Januzaj with the through ball, and Van Persie powered the ball past compatriot Maarten Stekelenburg.
United were away, which was the shot in the arm they dearly needed. The Red Devils had started slowly. But the spark provided by Van Persie had lifted the team, and they suddenly looked comfortable.
The Dutchman continued to link well with Rooney and Januzaj. All three players showed great movement together, anticipating the play well and showing knowledge of each other's games.
United then had a third in the 22nd minute when Van Persie squared the ball for Rooney to slot home.
Fulham had collapsed and were lucky not to go further behind when Rooney could only find the side-netting from a Van Persie corner.
Accurate through balls, strong finishing, good linkup play and accurate set pieces. That's a thoroughly complete performance, and if his goals last season didn't prove it, it showed how much United need Van Persie.
Rooney and Januzaj have stolen some headlines while the Dutchman has been forced to sit out. While they have both been magnificent, strong displays have sometimes come in spite of the team's overall performance.
With Van Persie in the side, United look so much more complete, having a potent attacking force as well. His goal today meant that Thierry Henry is the only foreign player to score more goals in the Premier League.
Yes, Van Persie's fantastic effort came against a side whose top three scorers have just eight goals between them. Even with his injuries, the Dutch forward now has nine.
Nevertheless, better teams than Fulham would have been undone today.
It seems that it is Van Persie, not Moyes, who will decide the fate of United's season.