The Red Devils warmed up for Sunday's derby with a 3-1 win over Villa on Saturday, with Ander Herrera netting twice and Wayne Rooney also getting himself on the scoresheet.
City, meanwhile, continued their torrid recent form with a 2-1 defeat away to Crystal Palace on Monday that left their hopes of retaining the Premier League title in tatters.
And Van Gaal insists that City's style of play makes them less problematic for United than Villa as the Red Devils look to boost their chances of getting second place.
“Villa were more defensive but I don’t expect City to play as defensively as Villa did, and then you need a lot of focus and concentration in defence,” the Dutchman told reporters.
“A long ball is very difficult to defend. But against City I don’t expect many long balls – and that is why I have less fear against City, in spite of the loss in the last game against them.
“On Sunday we have to wait and see if we can continue our good shape against City. I had more fear for Villa than City because every player shall be motivated and want to win.”
United lost 1-0 to City at the Etihad Stadium back in November after Chris Smalling was sent off, and Van Gaal warns his players must display cooler heads in the heat of derby battle this time around.
"I have started our preparation with talking about red cards – not the red card of Smalling,” he added.
“I am always warning in these kind of games that we have to control our emotion. We have had five red cards. Unbelievable. It is a record in my career as a manager. That is not good.
“Control of emotions is a talent. You have a lot of talents to have to be a professional player and you know when you have already a yellow card you don’t have to make a second foul to get a second card. You have to know that. But also that is a learning process.”