The Dutchman, who has scored 24 league goals this season, struck three times against Aston Villa on Monday as the club secured their 20th league title.
"It was fitting that United should wrap up the title up with a Van Persie hat-trick. There is no doubt that he has made the difference this season," McIlroy told reporters at a press conference.
"Losing the title in the final minute of last season to their fierce rivals Manchester City was a real killer blow, but all credit to Sir Alex [Ferguson] who vowed that it would never happen again. He knew that if Van Persie stayed fit this season then he would score the goals to bring the title back to Old Trafford.
"It is not an exaggeration to say that when he arrived at Old Trafford, Van Persie still had a point to prove. A first league championship medal and top scorer in the Premier League is vindication for Sir Alex and Van Persie."
Van Persie will return to his former club Arsenal on Sunday when United travel to the Emirates Stadium.