An injury to club captain Fede Valverde forced Mourinho into a change at right-back in Cantabria, after previously hinting at his preference for the Uruguayan over Trent as a long-term option.
However, the former Liverpool man benefitted from a show of faith by his manager, as he turned in an eye-catching display on Real Madrid's return to action.
"Trent was really good today. He hasn't played in a while, and he comes out and drops a masterclass; that's what happens when a team is confident and trusts each other.
"I thought Trent, with his technical skills, was the best option for this game, but that could change in other matches."
Up next for Real Madrid is a UEFA Champions League trip to AEK Athens on November 4th, followed by a league trip to Valencia four days later.