The retired Dutchman, who scored 150 goals in a five-year spell at Old Trafford, believes his countryman - who has already netted eight times in 13 appearances for the club - can give United the edge in their battle to win back the crown they lost to Manchester City last term.
He told The Daily Mirror: "As Robin is proving right now, he's making the difference on many occasions. If he can keep going like this through the whole season then I can see United landing another title win.
"I think he's fitted in really well at United. It's important for a striker when he goes to a new club to start getting his goals in early.
"That's what happened to Robin. He has the experience of the Premier League already and he’s proved to be a great signing, the way he plays."
|ROBIN VAN ONION-BAG|
|5/2||Robin van Persie is 5/2 with Bet365 to finish the season as the Premier League's top scorer|
The former PSV Eindhoven and Real Madrid striker was keen to praise Van Persie, who he feels has justified £24 million price-tag since joining the Red Devils from Arsenal in the summer.
Van Nistelrooy added: "I was close to him playing in the national team and I was convinced of his qualities then.
"It still has to work out, but hopefully he can go on and do even better. It's great to see, the way he plays.
"Robin fits into United's playing style. He's everywhere, involved in all of the play and the finishing as well, so that makes him special."