Martial is yet to return to the States following the birth of his second child as he looks for a move away from Old Trafford.
And the United boss also aimed a dig at Antonio Valencia, who has been tipped to skipper United this season.
The Ecuadorian has left the tour after limping out of an earlier pre-season clash with a calf problem, leaving United short of defenders.
“Antonio came from holiday, I think too much holiday for him, his condition was not good when he was back,” Mourinho said.
United face Real Madrid next up with Mourinho likely to be without Chris Smalling and Luke Shaw.
It means they face a defensive crisis ahead of their opener with Leicester, with the likes of Ashley Young and Phil Jones yet to return following their World Cup involvement.
Nemanja Matic is also set to miss the start of the season after undergoing surgery.