The Red Devils have gone behind in both of their Premier League games this season.
And Rashford admits United must not continue their sluggish starts.
"We have to use these three points as motivation to improve and keep getting better," Rashford told MUTVafter the win. "We have to improve if we want to hit our targets for the season.
"We had a slow start in the last league game and it's more important to pick up points. It's more important that we lost the first league game, we had to win today.
"It doesn't matter how we won, we got the three points and we'll move forward and improve."