Stam insists the Dane's form issues is down to the United manager.
He told Makthavare.se: "I think that it’s the style of play that is holding Rasmus Holjund back.
"We don’t know how the manager is trying to use him in matches and I think he doesn’t get a lot of chances to touch the ball and get into games.
"It becomes a very difficult situation for a striker because you don’t see crosses coming into the box and the emphasis should be on creating chances for him. If you don’t get chances you can’t prove how good a striker you are."
Former United defender Stam admits he is also disappointed seeing Marcus Rashford away on-loan at Aston Villa, where he is now thriving.
He continued: "It's sad to see Marcus Rashford in an Aston Villa shirt because I thought he would be a very important player for Manchester United and stay for a very long time.
"For me, he cannot be considered a legend at Manchester United, I think he left too soon to be considered as one.
"When you look at all his seasons at the club and for how many he performed at his best, he had one season under Erik ten Hag in which they changed the style of play and he scored a lot of goals and was a danger to every defence he faced.
"He got a new contract and everybody expected his form to carry on, but to be considered a true United legend you have to show that form for seven, eight or nine seasons.
"That is the level you need to reach to be considered a legend."