After an injury-disrupted first year in Madrid, Mourinho has consistently opted against starting the 28-year-old at right-back, with Denzel Dumfries and club captain Fede Valverde ahead of him.
An injury for Valverde brought Trent into the starting XI for today's LaLiga clash at Racing Santander, but Mourinho remains unconvinced, as Chelsea reportedly eye up a bold January offer.
Mourinho stated he continues to have faith in both Trent and Dumfries, but he feels Valverde is a better fit to the role, as he looks to reshape his Los Blancos squad.
"It hurts me. I don't like giving bad feelings to players; I prefer them to feel good. When you build a squad with two players per position, and end up playing a third, it's not something I like.
"But there are things more important than these feelings, things that matter more for the team at a given moment.
"I feel we needed to change our midfield and play Fede in that position. It was a decision made for the team, not based on individual players."