United were disappointing in the second half, having failed to carve out a serious opening in the final third.
And afterwards Mourinho asked Pogba, Lukaku, Jesse Lingard and Marouane Fellaini - the players still recovering from the World Cup in Russian Federation - to make themselves available at Old Trafford on Friday.
According to the Mirror, United's pursuit of both Ivan Perisic and Willian have stalled and have left the club unwilling to sanction any potential exit for Martial with a replacement looking unlikely prior to the close of the window on Thursday.
Instead, United did not manage a single shot on goal against a team who only returned to training 10 days ago.
Javi Martinez headed home a second-half victor to give Bayern victory in a match they dominated.
And while Mourinho is glad to see the back of pre-season, he did reserve some praise for how his youthful side handled itself against worldwide stars.
"The players were, once more, brilliant". "And with the fantastic spirit we have, in the majority of the players, I repeat: in the majority of the players, we have a fantastic spirit, we go with everything we have to the Premier League". We don't want to come here and to lose badly, four or five.
"I found out that Martial was going to Paris when he told me", said Mourinho at the time.
"If we don't make our team better it'll be a hard season".