United host Astana from Kazakhstan in their Europa League opener on Thursday, with boss Ole Gunnar Solskjaer expected to rotate his squad and bring in some youngsters.
“I very much like them," said Mata. “I could speak about every one of them.
“Gomes – very talented. You can see he's a real football player: vision, decision-making, quick on his feet.
“Chong is a proper winger. Very quick one-against-one, a very nice left foot and a great shot.
“Jimmy Garner I like very much. Composure, personality on the ball, good shot, good decision-making. He touches the ball just the times he needs to.
“As a midfielder that's important – not just to retain the ball a lot, but to make it move quicker, and he does it so much.
“Mason is a very good finisher, both legs. You can't really tell if he's right-footed or left-footed, which is a very good quality for a striker.
“All of them have been training with us for a long time and they developed a lot in pre-season.
“Football is not about age. Even for me. I'm now 31, but I don't think I'm old for football.
“I feel very young in my mind, in my legs. So football is not about age. It's about quality and the capacity you have to show it."