Matic has been linked with a return to Stamford Bridge this season.
Mourinho said: "Matic is a good player. Currently he looks solid and mature. He is wise and stable. He is a player that looks very mature on the pitch.
"Benfica is a big club and he seems comfortable. I don't see any interest from the club to want to sell him. It's very nice to have players like these in Portuguese football."