The Spain international was widely praised following his man of the match performance in Manchester United’s 3-1 win at title rivals Arsenal at The Emirates earlier this month.
De Gea equalled a Premier League record with 14 saves during Manchester United’s triumph in north London to help secure three points in the top of the table clash.
The 27-year-old shot stopper made five stops during Manchester City’s comfortable 2-1 win against Manchester United at Old Trafford in the derby on Sunday evening.
De Gea has been linked with a move to Real Madrid on a regular basis over the past three or four seasons but a deal has failed to materialise despite his ties to the English capital.
The Manchester United number one didn’t even make Fifa’s best goalkeeper shortlist as Gianluigi Buffon won the award for his heroics in Juventus’ run to the Champions League final.
The Red Devils talisman finished in 20th place in the Ballon d’Or voting as Manchester United legend Cristiano Ronaldo won the accolade for the fifth time.
Speaking to Manchester United’s website about De Gea, Mata suggested that the Spanish shot stopper doesn’t get the international recognition that he deserves.
“You know, everything has been said about David from journalists, ex-players, current players, from myself,” Mata said.
“He is great. He is fantastic. He has an incredible talent and has shown that in every single game in every single season, which is so difficult to do. His consistency is what makes him the best or one of the best, for sure. He showed it on a big stage like Arsenal as he made sure we got the points.
“You know what?” he continued. “I don’t know why some people don’t appreciate him and how good he is. He’s not always on the list of the best goalkeepers in the world, or whatever these awards are, and, for me, it’s definite.
“I see his games week in and week out and can see he is great and fantastic. He has to be in the top three, top two or top one. For me, he’s the best and it would be nice if more journalists, not just in England as he is very well appreciated in England, but in different countries, realised how good he is.”
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news