Northern Ireland defender Jonny Evans will be sidelined for the "next few weeks" due to a thigh strain he suffered in the first half of United's 4-3 Champions League defeat at FC Copenhagen.
Manchester United said late on Friday.
He joins a lengthy injury list at United, who remain without defenders Lisandro Martinez, Luke Shaw, Tyrell Malacia and midfielder Casemiro.
The 35-year-old will miss Northern Ireland's final Euro 2024 qualifiers against Finland and Denmark. Northern Ireland, who sit fifth in Group H with six points, travel to Finland next Friday before hosting Denmark on November 20.
Evans rejoined United on a one-year deal in September, eight years after leaving Old Trafford and has started five league games.
United lie in eighth place in the top-flight after picking up 18 points in 11 matches and host promoted Luton Town later on Saturday.
Joao Cancelo and Joao Felix scored in each half to earn Barcelona a 2-1 comeback win at home against Porto on Tuesday that booked their spot in the Champions League knockout rounds for the first time in three seasons.
Manchester City's Julian Alvarez scored in the 87th minute as the European champions clawed their way back from two goals down to beat RB Leipzig 3-2 and clinch top spot in Champions League Group G on Tuesday with one round of matches remaining.
Glenn Maxwell's blistering century trumped India opener Ruturaj Gaikwad's unbeaten 123 as Australia clinched a last-ball victory in a thrilling third T20 International to stay alive in the five-match series on Tuesday.
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