The Leicester City striker will break the former Red Devils marksman’s 12-year record of 10 consecutive League goals if he scores against United in today’s clash at the King Power Stadium.
Vardy’s goals have propelled the Foxes to the top of the table, and Van Gaal believes a comparison can be made between him and the former Dutch international.
“More or less, Van Nistelrooy is like Vardy,” the United manager tells Sky Sports.
“He is highly concentrated to make goals and is always running in behind, so you can compare them.”
Having said that, Van Gaal also believes his defence is well equipped to nullify the threat of the England striker.
“He was last season [when we lost 5-3 to Leicester] a very nasty player for us,” Van Gaal added.
“He scored, won a penalty, and now he is scoring 10 games in a row, then you are a great player.
“I only know Dennis Bergkamp as a player who did the same with Ajax. It's not so easy to do that.
“He is a player who is difficult to defend. It shall be difficult I think, but we can do that because we have a lot of clean sheets already.”
Leaders Leicester City against second-placed Manchester United kicks off at 19h30.