The Englishman has suffered a host of injuries that have kept him from cementing his place in the starting XI under Mourinho.
He came off at half-time during the 4-1 victory over West Ham in the EFL Cup win even though it was his only his second appearance in November.
Speaking in his press conference ahead of the clash, Mourinho insisted the injury was a pity.
“The injury is a pity,” he said.
“We were on this process of developing him as a player – he has a lot to learn and great potential to develop so we were giving him 90 minutes.
“Not consecutive matches but 90 minutes against Feyenoord then, one week later, 90 minutes against West Ham, but he got this little injury.”
Shaw has worked himself into a big role at United and although Matteo Darmian has performed at left-back, he hasn’t been able to fill the Englishman’s shoes.