Van Nistelrooy netted 150 goals in just 219 games for United between 2001 and 2006 and believes the former Arsenal striker (whose current strike-rate almost mirrors Ruud's 0.68 goals per game) can score just as many.
"I hope so," Ruud said. "My time has gone and now others have taken over, so I hope he does [score as many as me].
"Robin has proved he's fitting in easily. It's like he has always played for the club.
"He didn't need any time to settle in. He was straight on his level, scoring important goals and winning games for the team."
Van Nistelrooy was in Manchester last week for Sir Alex Ferguson's statue unveiling and admits he caught up with United's current Dutch striker during the trip.
"I spoke to him [before the statue ceremony]," he said.
"He feels very good at the club. But that's the feeling everybody gets when you come here. I felt the same. I felt very comfortable.
"You feel part of the family and of a tradition. You just want to go out and perform and Robin's doing that now."
Although van Nistelrooy and the United manager had their differences towards the end of the Dutchman's spell at Old Trafford, Ruud says the pair's relationship has been repaired now and he's confident Sir Alex will help Robin van Persie thrive at the club.