The Red Devils have already played 63 football games this season and have been hit by some serious injury problems.
However, Mata is not worried as he thinks every United player will be up for the final.
"We have the chance to win the biggest thing since I came to the club. It's been a long season, but when you have a game like this, all the fatigue and tiredness in your legs and body goes away. It's not a normal game, it's a final."