The centre-forward came into his own last season and was one of the stars of France's run to the final of the Olympic Games this summer.
Morrison, who has deep connections at Palace, tells Tribalfootball.com that management are delighted seeing Mateta now living up to his potential.
"To be fair, he has been outstanding," said Morrison. "(Technical director) Dougie Freedman said it to me, when Jean-Philippe Mateta gets a run of games, then he will be exceptional.
"He had a tricky start because he was in and out of the team, any striker will tell you that you need a run of games to build up your momentum.
"Odsonne Edouard was playing three games, then Mateta came in but then of a sudden along with (Oliver) Glasner arriving he made him the number one striker.
"He hasn't looked back since, he's been fantastic, he's a handful and he's a big target man who can run in behind and score goals.
"He's like a complete centre forward who you want at the moment, so long may that continue.
"Listen, there will be clubs knocking at the door if he keeps up the form, but I think it's definitely one player they keep a hold of this season.
"Fair play to him, sometimes as centre forwards you gets judged on your goals and if you're good enough.
"He's knuckled down, put the work in and now he's showing his worth."
As Morrison mentions, interest is growing in Mateta - just at a time when captain Marc Guehi appears to have one foot out the door at Selhurst Park. The chances of the England defender moving to Newcastle gathering momentum this week.
"Listen Newcastle United are a big football club and they've got a very good manager in Eddie Howe, so it would be a good move for him personally," Morrison reasons.
"But I would love for him to stay at Crystal Palace for at least another year.
"Football has changed massively these days; you don't have to play for the top teams to be an England international.
"Marc Guehi went to the Euros and was one of England's stand out players when people were questioning whether he could step into Harry Maguire's shoes.
"I think he did that and more, he was brilliant alongside John Stones.
"People forget he had an injury towards the back end of the season, came back in and was outstanding.
"I can only speak so highly of him, he's one of the nicest guys you'll come across and when you speak to him, he's such a humble guy.
"He just wants to keep learning, wants to improve and wants to get better as a player, so the world is his oyster.
"But please, another year at Palace then I would understand one of those top four teams coming knocking on the door.
"If Newcastle pay Palace the money they want, then there's always the chance he leaves, but I hope he stays because he's a class act."
- Clinton Morrison was speaking to Tribalfootball.com on behalf of Betway