Even though the Spain star only completed his club record £37.1million move from Chelsea on Saturday, manager David Moyes still felt confident enough in him to start Tuesday's Premier League encounter with Cardiff.
Although Mata was not at his very best, the early signs were encouraging and United's 2-0 win very welcome given the difficulties they have endured this season.
Young feels the process has been assisted by the welcoming reception Mata has received from his new team-mates.
"Juan looked like he had been here for years," he said.
"He had only been training for two days and it was his first game but he has gelled straight away.
"There is a great team spirit here. There are some great characters and the banter is brilliant. I have never experienced anything like it.
"When he has fully settled in he will add something special to the squad."
Mata will never have to go through the kind of United initiation David Beckham endured.
Beckham recently revealed he was forced to perform a sex act on himself standing in front of a picture of former Red Devils star Clayton Blackmore.
These days, singing a song is a more likely forfeit, although Mata's arrival has been so recent, he has not even had that to do just yet.
"There might be (an initiation)," said Young.
"I am not sure when it has to happen - or if it does. We will have to wait and see."
Without even trying though, Mata has provided the spark United so desperately needed.
As Phil Jones pointed out, his team-mates are already trying to impress the new boy and Young confirmed the dressing room seems a slightly more positive place.
"It has lifted everyone; the fans, the staff and the players," he said.
"Obviously, as it is the transfer window, you are wondering who is coming in and what is going on. When you see a player like Juan Mata coming in it is fantastic.
"He is one of those world-class players who can fit into any team."
Young's response was a positive one.
Whilst it seems fellow wide man Nani might be heading for a loan spell at Inter Milan, having failed to find the form that persuaded Moyes to hand him a new five-year contract as recently as September, Young sparkled on Tuesday, drilling home an impressive second-half goal that wrapped up the win.
"It was not too bad," said Young.
"You have to be on the ball. You have to put in performances every week. It keeps you on your toes.
"Manchester United has a big squad, we can rotate the team. It ensures you keep wanting to play well, wanting to train well.
"That is the only way to keep yourself in the team and in the manager's thoughts."