Man United fans will hope the youngster is finally starting to realise that Mourinho doesn't accept slackers.
Mata, who underwent surgery on Friday, admitted he had found being reduced to the role of a spectator hard.
Midfielder Mata, who has struck 10 goals in all competitions this season, is unsure when he will be fit for a return to action, but feels support from fans has given him a boost. "I came with the team as it was", he said in an interview with MUTV. "I have been winning but If you want to win bigger you have to create bigger".
Manchester United will continue their quest for a top-four finish in the Premier League when they welcome Everton to Old Trafford on Tuesday.
With United sitting four points behind rivals Manchester City in fourth position, Mourinho will need a massive effort from his club over the season's final nine league matches to equal the feat of his Dutch predecessor.
Mata believes the club have been unfortunate with the number of absent players in recent weeks. We can not score a goal even when we are one on one.
United manager Mourinho welcomed top scorer Ibrahimovic and Ander Herrera back from suspension, while Paul Pogba returned to the bench following a hamstring injury.
The Toffees make the midweek trip looking to bounce back from a disappointing 3-1 defeat to Liverpool in the Merseyside derby on Saturday - only their second loss in 2017.
"Before I was more emotional and deep into my feelings when I had to watch on from the sidelines, but now it is more that I look at the game and I have trust in my team-mates, I have confidence in them".
"Romelu, it was hard".
"(But) he's the top-scorer of the league.
At that point we can presumably hail Mourinho has a genius for getting good things out of the most expensively assembled side in history? He's a great striker, he's working hard.
Ibrahimovic's last-gasp spot-kick - his 27th goal of the season - meant United held on to fifth place, three points above Arsenal and Everton having played a game more than the former. Shaw has shown that he has the capabilities to be a great player, and with one year left on his contract, he needs to show that he deserves a run in the first team. Of course, he lost several balls in the midfield, instead of playing a little bit faster and no dribbling with the ball.
"I have probably one, two or three years".
"It's easy to give your opinion in front of the television without any responsibility".
Ronald Koeman's side were criticised by Reds boss Jurgen Klopp but the Dutchman defended team's approach. They had chances to score.