The Welshman, on loan from Real Madrid, has made only four Premier League appearances in 2021, starting just once.
"He doesn't need to convince me of anything. I am totally convinced about everything," Mourinho said. "It's not about convincing me, it's about being ready to play the minutes we all would love him to play.
"It's a process. You feel that in matches in the last couple of years. It's the process. We want him of course to be ready to play every minute of every game.
"He is a player with special qualities, you could see against West Ham in the second 45 minutes the positive impact in the quality of the game. He had a cross, he had a couple of assists, he hit the crossbar.
"He is doing that better and better, but he is not playing 90 minutes, he is not playing every game. We have to manage his evolution, but he has nothing at all to convince me about."