The Real Madrid loanee earned a start against LASK last week, and although he hasn't started in the Premier League yet, Europe could present him with another chance.
Another start could also be handed to Carlos Vinicius, another summer signing from Benfica.
Serge Aurier and Steven Bergwijn missed Monday's win over Burnley, and although they might not be fully match fit they could start as Mourinho will likely freshen things up with the team having played just a few days ago.
Erik Lamela and Harry Winks are another two who could start.
Dele Alli wasn't even in the squad for the game against Burnley, but should return to the bench for European duty.