Manchester United could be without midfielders Nemanja Matic and Marouane Fellaini for their upcoming trip to Arsenal on Saturday (2 December) after the former suffered a muscular problem in the win against Watford, while the latter sustained an unspecified injury before the clash against the Hornets.
Matic started his side's 4-2 victory over Marco Silva's side on Tuesday but was replaced by Ander Herrera on 54 minutes after suffering a knock. The Serbia international was able to walk off the pitch at Vicarage Road and looked in some discomfort as he took his place in the stands.
Mourinho, who will be hoping Michael Carrick will be available to feature against Arsenal on the weekend after overcoming a minor heart problem, was not optimistic regarding Matic's injury and seemed slightly concerned about United's shape and lack of defensive stability in the 29-year-old's absence.
"For Nemanja Matic to tell me he wants to be replaced, he does not do that if it's nothing important. It is muscular," Mourinho said in his post-match press conference.
"What we need to do is go back to our defensive stability, which we lost when Matic had to come out. But the important thing is the three points. I saw happiness from the team and they played with a free mind."
The injury to Matic followed news of Fellaini's knock. The United star, who only recently returned from a knee problem that kept him out for almost a month, was not a part of the squad for the match against Watford, with Mourinho revealing that the former Everton star had picked up an injury before things got underway in Hertfordshire.
Asked if Fellaini had picked up an injury, the United told NBC Sports ahead of kick-off: "Yes." When pressed about the Belgian's potential availability for the clash against Arsenal, he added: "I don't know."
The injuries to Fellaini and Matic could not really have come at a worse time for United, who face Arsenal and runaway league leaders Manchester City in the next week or so. Carrick is believed to be closing in on a return, but the Belgian and Serbian's prospective absences will presumably shift an even bigger burden onto Paul Pogba, who has only just returned to action from a serious hamstring injury that sidelined him for two months.