Rashford struck from the spot to send United on their way to a 2-1 win.
He later remarked: "I tried to stay calm and get the first goal. It's an important moment in the game, the main thing is it put us in a good position as a team. I had one from Fred that I misplaced and had one off the bar, so that could have been three or four goals up.
"It's been an inconsistent start to the season, it's a young team, and we've been trying to get the right fundamentals and the only way to get consistency is to go through these hard times. You have to stick with the manager and process. If we do that we've got something to be excited about in the future."