Jose Mourinho's men were beaten by Huddersfield Town last month as the promoted side took advantage of United's defensive mistakes to score two quick first half goals and England international Rashford is wary of a repeat against Brighton.
"When we're playing such attacking football, you might sacrifice some other things that you need. If we get those two bits together, then that's the ideal situation," Rashford told the club's website ahead of Saturday's clash against Brighton and Hove Albion.
"I think against Newcastle in the first half we were a bit too open because of how freely we were trying to play."
The 20-year-old has warned United not to underestimate a Brighton side that have a solid identity and gameplan that has led them to ninth in the standings.
"Brighton are doing well and it will be a difficult game," Rashford added. "I think when teams come up, the most important thing for them is that they have identity and they have a plan of how they play.
"As you can see, Brighton have that are building on each performance and getting stronger.
"These types of games can be underestimated (by some) in terms of how difficult they are, but we know as players it will be tough and we'll be ready."
(Reporting by Aditi Prakash in Bengaluru)
