Manchester United lost 2-1 to Young Boys on Tuesday night after Aaron Wan-Bissaka was sent off. Jesse Lingard also made a huge mistake in preparing for the late Young Boys winner.
Captain Harry Maguire has said United need to eliminate the mistakes.
“Of course, discipline is an integral part of tournament football,” said Maguire.
“For example, if it was a knockout game and we come out of the competition because we’re down to 10 men, I’m sure everyone will hit each other.
“It’s fortunate that this is the group’s first game and we have a lot of time to bounce back.
“As far as Jesse is concerned, obviously no footballer likes to make mistakes, but it is an integral part of the game.
“We are humans, every footballer makes mistakes, we will learn from them, they will learn from them.
“He will get up and be ready to go on Sunday because that is such an integral part of football.”