Marouane Fellaini admitted he had to "control himself" after picking up an early booking against Celta Vigo, a week after seeing red in the Manchester derby.
The Belgian international is relatively fresh for the Europa League ties due to missing his side’s league games with Swansea, Arsenal and Tottenham through suspension.
"We had control and we knew what we had to do," Fellaini told MUTV.
"We created chances in the first half and we deserved the goal.
“After an early booking and my red card against Manchester City last week, I know I have to have greater control.
"It will be tough [in the second leg]. They are a good team. We have to give everything on Thursday, give everything to get to the final.
"We have a lot of injuries. It's difficult because we have a lot of games and we give everything in every game. We have to keep going and win at Arsenal [on Sunday].
"We have the players and the team and we want to do that."
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