United captain Rooney has scored just twice in 11 Premier League appearances this term but is expected to be in the starting line-up when his team-mates play leaders Leicester City on Saturday.
Manager Van Gaal denied he selects Rooney because of his role as skipper and instead highlighted the benefits of picking the 30-year-old striker.
"Wayne is doing a lot, has a very great contribution in the team. I am very satisfied with him," the Dutchman said.
Asked if Rooney is worthy of his place on merit, Van Gaal added: "Yes, of course. Otherwise he is out of the team.
"At this moment, he doesn't play in the striker's position, [Anthony] Martial is playing there. But it is possible he shall play other matches there. It depends not always on the quality and shape of the player at the moment, but also the game plan."
In contrast to Rooney's misfortune in front of goal, United will come face-to-face with the league's sharpest finisher at the King Power Stadium.
Jamie Vardy has scored in a record-equalling 10 consecutive league games to take his total to 13 for the season and Van Gaal acknowledged United must be prepared to be tested.
"Vardy is difficult to defend against," he conceded.
"It was like that last season and even more so now. Vardy is like Van Nistelrooy - highly concentrated to make goals and always running in behind.
"It shall be difficult to stop him but we can do that because we have a lot of clean sheets already."