The Real Madrid attacker's return to Spurs has seen the Welshman starting just two Premier league games so far this term.
Speaking about the situation, Mourinho said: "I cannot give players minutes – minutes on the pitch is not something I can give.
"We all know the difficulties that he had for a couple of seasons.
"We all know that he arrived injured, we all know that even this season [he is] a little bit up and down with small things
"The most important thing for him is to be consistent in training, at high intensity without any problems, and when a player is consistent in training then the player is ready, not to be given minutes but to earn minutes. That's a different thing."