Mata opened the scoring in United's Carabao Cup win against Luton Town FC.
The Red Devils returned to winning ways when they travelled to Kenilworth Road.
Manchester United midfielder Juan Mata said the Carabao Cup win against Luton on Tuesday night was vital after their abysmal display in their Premier League opener against Crystal Palace.
United sealed a 3-0 win over the Hatters, thanks to goals from Mata, Marcus Rashford and, Mason Greenwood.
It was a deserved win for Ole Gunnar Solskjaer’s side, although, it took time for United to get a grip of the game.
Speaking to Sky Sports after the game the Spaniard said: "It is one of those games where if you win you did what you had to do and if you lose it's a mess. We did a professional job today, we didn't concede a goal, we scored three goals and we played some good football. It was important to win after our first game in the Premier League which we know wasn't good enough."
On goalkeeper Dean Henderson, who made an important save when it was 1-0, Mata said: "It was very important because it was 1-0. He did a great save and somebody also cleared the ball on the line.
"I think we did OK. We have all not been training together for too long and now it is important to get the rhythm back and to get confidence. The confidence comes with results."
On the fitness of the Man United squad, he replied: "To be honest I felt fine and I think most of the guys felt OK. I think we did OK physically but for me, it is very important in the mind - if you are confident and if you believe in what you are doing and get results then the body will follow."