Both have featured in the Champions League this season, and McTominay was included on the bench for the Manchester derby last Sunday.
But Mourinho is ready to hand the youngsters more responsibility with games coming thick and fast over the next four weeks.
"I have faith in them," the manager told MUTV.
"Honestly, sometimes, I don't play them more because I have respect for some of the older players that are great professionals and are always ready for the team.
"But, in terms of their qualities, McTominay and Tuanzebe are ready, they are ready to play so I played them with 25, 30 minutes to go against CSKA. I played Scott against Benfica when we had not even yet qualified. I have lots of faith in both of them."