The Dutchman, who had been the early favourite to win the PFA Player of the Year award after his blistering start to life at Old Trafford, has not netted for the Red Devils since February 10 against Everton.
Sir Alex adamantly told reporters: "Listen, Van Persie was fantastic on Monday [against Manchester City]. Along with Phil Jones, he was our best player.
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|5/1||Robin van Persie is 5/1 with Bet365 to score two or more goals against Stoke City
"For this year, I don't watch all of the players all the time but, if I had a vote, Van Persie would surely be up there."
Despite his barren run, Van Persie has still scored at a rate of over one every other game in United colours this season, netting 23 in 41 appearances.
He will get a chance to improve that record at Stoke City on Sunday but Potters boss Tony Pulis warns that the league leaders would be wrong to underestimate the difficulty of their task at the Britannia Stadium.
"We make it such a tough place to play at," observed Pulis. "We've also done well against the top teams.
"It has a lot to do with the atmosphere at the Britannia and I think the crowd will be up for it."