The three-time Manchester United player of the year was on his way to Real Madrid in 2015 during the summer transfer window only for his transfer to collapse unusually on the deadline day.
De Gea signed a new contract at United after the debacle, however, this season again it is up in the air that the 26-year-old is poised to join the bitter rival of his former club Atletico Madrid.
The Spanish keeper has reportedly also put his £3.85m luxury mansion in Bowdon up for sale igniting the talk of a big-money move to Madrid more.
However, Mata has suggested that the custodian still has a lot to offer at Old Trafford and sees no reason for his colleague to attempt an exit from Old Trafford.
"Well, I think he is happy and I think he is obviously committed to the club. He has got a contract," Mata said.
"He is obviously more than used to living England, he is happy in Manchester. For me, he is great – great person, great player. If not the best goalkeeper in the world, top three for sure.
"He gave us a lot of points during the last seasons, player of the season for the team, and obviously, he is happy and I don’t see a reason for him to change. So let’s hope that he can save so many more goals for us."
Should the Spanish number one leave, Jose Mourinho has reportedly zeroed on a number of options including Atletico's Jan Oblak and Leicester City's Kasper Schmeichel.
De Gea will be returning to the starting lineup again on Sunday (May 14) against Tottenham Hotspur.