The Dutchman, whose side head into the game on the back of their 3-0 win over Everton in their most recent Premier League outing, believes that the Citizens are set to benefit from a favourable Champions League schedule in the lead-up to the game at Old Trafford.
United faced an eight-hour round trip to Russia to take on CSKA Moscow in the Champions League on Wednesday night, while local rivals City hosted Sevilla at Etihad Stadium.
And the United boss believes that the schedule leaves City with a clear advantage ahead of their trip to face their fierce rivals.
Van Gaal told a news conference on Tuesday: “Every club at the top of the league has the same problems. But now Manchester City has a benefit because they are playing at home and that is a difference.
“You have the benefit of the recuperation. Manchester City don’t have the travel we have so they have more rest. There is nothing you can do. They have the benefit.
“We do a lot of things to try and help. We have cold baths, we have warm baths, less training sessions and practice so the freshness is good enough to beat City.”
United head into Sunday’s game in third place in the Premier League table and two points behind leaders City.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news