Manchester United have revealed that both Zlatan Ibrahimovic and Marcos Rojo have both sustained "significant knee ligament damage" to effectively confirm that the duo will miss the remainder of the season.
Rojo was stretchered off midway through the first half before Ibrahimovic landed awkwardly in the final seconds of normal time, though he was able to limp down the tunnel.
A statement read: "Detailed investigations on the injuries sustained by Marcos Rojo and Zlatan Ibrahimovic during Thursday's Europa League match have confirmed significant knee ligament damage in both players that requires specialist opinions over the coming days.
"Estimations of time to full recovery will only be possible once definitive treatment plans have been decided after these consultations."
Goal revealed on Friday that Ibrahimovic will definitely miss the rest of the season, with some reports even suggesting he could be out until 2018, casting doubt on his United career.
The Swede is yet to commit to a second season at Old Trafford, and it remains to be seen as to whether the offer that was previously on the table for the 35-year-old remains following this setback.
Rojo's injury, meanwhile, further adds to the defensive headaches Mourinho has suffered in recent weeks with fellow centre-backs Phil Jones and Chris Smalling already on the sidelines.
Eric Bailly and Daley Blind are United's only fit senior central defenders, and Timothy Fosu-Mensah and Axel Tuanzebe could earn opportunities before the end of the campaign.