After returning from injury, Mateta has quickly hit his goalscoring straps.
Ahead of tonight's Europa Conference League quarterfinal second-leg clash at Fiorentina, Glasner said: "I am very pleased to have him back and getting closer to his best fitness. I think he is not still at 100% but he is coming closer and closer.
"To be honest, it was very easy to manage him because he is a lovely person, first of all, and he is a great football player.
"He said: 'Gaffer, I will work very hard to be fit and help the team achieve our goals' and this is what he did from day number one.
"I think everybody in the dressing room, everybody at Crystal Palace, likes him because he is just such a lovely person and a funny person. He is always joking, smiling, and he is just bringing good mood to the dressing room."