Rooney is banned for the club’s next two matches, against West Brom on Monday and Chelsea next weekend, having been sent off in the 2-1 win over West Ham on September 27.
He is due to return against cross-city rivals Manchester City on November 2, but Van Gaal insists he will not start the game unless he impresses in training.
“Nobody is walking back in my team, believe me. You have to earn it on the training ground,” he told reporters.
“But every player here already knows that. I have always said that just because players have the best name, it doesn’t mean that they are the best for the team.
“I am always looking for a constant level of performance – from the team and from individual players.”
United have been hit by a number of injuries this season, with Michael Carrick and Phil Jones notable absentees, but Van Gaal has been impressed with the players who have been drafted in to provide cover.
The Dutchman has handed first-team berths to Patrick McNair and Tyler Blackett, among others, and has praised the young stars.
“Wayne Rooney, Michael Carrick and Phil Jones are great football players but, believe me, sometimes the other players are doing better,” he added.
“It is not only the name. I have seen, for example, a player like McNair. He was outstanding in the first match and you have seen the reaction of the fans to that.
“Of course Phil Jones, Jonny Evans and Chris Smalling have not been available. But I am always thinking that youngsters can take the job over. It’s not any problem.
“We have also good youth players – and we have showed that already with not just McNair but with Blackett and also with Jesse Lingard. Their progress is more quicker than you think.”