The Englishman played the full 90 minutes in the victory over Fenerbahce on Thursday night, but surprised supporters after he didn’t even make the bench at Stamford Bridge.
Rooney would have been unlikely to start against Antonio Conte’s side after his participation a few days earlier and his demoted role from the starting XI in recent times.
Speaking ahead of the game, Mourinho confirmed Rooney is missing after suffering a thigh problem in the last training session before the match.
“Injured in training in the last session,” he said.
“He was feeling it in the game against Fenerbahce, he was so keen to play for 90 minutes he hid it, felt it a little bit in the training session, and he couldn’t come.”
It remains to be seen whether he will be fit enough to face Manchester City at Old Trafford in the EFL Cup on Wednesday night following his new setback.
After a decent showing against Fenerbahce, hopes were Rooney would be able to build on his performances, but it’s all gone for bad to worse for the Englishman with his latest injury.