The defender, handed the club’s ‘Player of the Month’ award for August, picked up a concussion during England’s 1-2 defeat to Spain at Wembley last weekend.
Reports have suggested that Shaw would be cleared in time to face Watford and would instead return against Swiss side Young Boys next week.
But Mourinho, speaking at a press conference, noted that from a medical point of view Shaw was free to play the game.
“I don’t know – we still have a training session,” he said.
“Contrary to some news, to some opinions, by the protocol point of view and according to our doctor, he will be free to play.
“The only situation we have to analyse is if you are going to play him when, during the week, he was not training with the team or if, even so, he decides to play.”
Mourinho also confirmed that midfielders Marouane Fellaini and Ander Herrera are both doubts for the game. New signing Diogo Dalot and forgotten man Marcos Rojo, on the other hand, will both play for the Under 23s against Reading tonight before returning next weekend.
“Fellaini is a doubt. Ander Herrera is out. He had one little problem in one medical in training during the week, so he is also a doubt.
“Diogo Dalot and Rojo play tonight with under-23s and if they play 90 mins like we expect, it will be the end of their recovery process and we will consider them ready to be back next week for full competition.”