The Red Devils made it two wins out of two in the Champions League after their 4-1 win over CSKA Moscow on Wednesday (27 September) to take them to the top of their group.
However, Anthony Martial, who scored and provided two assists for Romelu Lukaku, was taken off after 72 minutes with a thigh problem.
The former Monaco man was due for a scan on Thursday (28 September) and Jose Mourinho is expected to throw more light on the injury at a press conference on Friday (29 September).
Martial is not the only problem though, as United also travelled to Russia without the likes of club captain Michael Carrick, Antonio Valencia, Marouane Fellaini and Phil Jones.
Mourinho did not offer any update on Valencia but did provide news on the other three players who did not travel for the win in Moscow.
"Carrick has no chance," Mourinho told BT Sport, as quoted on the official Manchester United website. "I think Jones I have many doubts. And Fellaini I have a hope, just a hope."
There was no update for Paul Pogba either who will be missing from action at least until next month after suffering a hamstring injury in United's Champions League opener against FC Basel.
The Frenchman started the season in red-hot form with two goals and two assists in four league games but has now missed the club's last four games in all competitions.
The other long-term absentee is Marcos Rojo who is recovering from a knee injury.
Manchester United host winless Crystal Palace at Old Trafford on Saturday (30 September) as they will be hoping to make it six wins out of seven league games this season.