Manchester United say Northern Ireland defender Jonny Evans will be ruled out for the "next few weeks" after picking up a thigh strain.
The 35-year-old is now set to miss Northern Ireland's final Euro 2024 qualifiers against Finland and Denmark.
Evans was forced off after 13 minutes in Wednesday's Champions League defeat in Copenhagen.
Northern Ireland travel to Finland on 17 November before hosting Denmark in their final qualifier three days later.
United manager Erik ten Hag had said earlier on Friday that the defender, in his second spell at the club, will miss Saturday's Premier League match with Luton but he could not say if he would be available for Northern Ireland duty.
However, further scans revealed the extent of the injury and Northern Ireland manager Michael O'Neill is now set to be without one of his most experienced players.
Northern Ireland cannot qualify for the finals in Germany but O'Neill has spoken about the centurion defender's importance as he looks to develop a youthful squad.
Ten Hag will have Victor Lindelof back in his Premier League squad after the defender missed the win over Fulham through illness, while Raphael Varane could also fill in for Evans.
United's first match after the international break is away to Everton on 26 November.