Ulster have confirmed Ethan McIlroy has undergone surgery to repair a torn ACL.
The 24-year-old suffered the injury in last month's Champions Cup defeat to Leicester.
There's better news on James Hume, Stuart McCloskey and Jacob Stockdale, with all three players back in full training.
Meanwhile, the province has also confirmed the departure of defence coach Jonny Bell.
He's set to leave his role to take up a position outside of rugby.
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Cadan Murley has been ruled out of England's clash with France on Saturday in the Six Nations due to a foot injury.
The Harlequins wing picked up the problem in their opening 27-22 defeat in Ireland on Saturday.
Saracens centre Alex Lozowski has been added to the squad as a replacement.