Eric Bailly is set to be on the sidelines for around "two or three months" after Jose Mourinho confirmed that the Manchester United centre-back will require a surgery on his troublesome ankle.
The 23-year-old centre-back originally picked up the injury while on international duty with Ivory Coast in October.
The former Villarreal defender was able to return to action weeks later and played the full 90 minutes in the clashes against Tottenham Hotspur, Benfica and Chelsea.
However, the United centre-back has not been able to feature for the 20-time English champions since the defeat to the Blues at Stamford Bridge on 5 November.
Earlier this week Mourinho revealed that he had a "serious injury" and the boss has not confirmed that will need to undergo an operation to address the issue.
"Bailly goes to surgery – the decision is made. I don't say [he's out] for the rest of the season but it's for the next two or three months," Mourinho confirmed to MUTV ahead of the Premier League trip to West Bromwich Albion on Sunday (17 December).
The news is a major blow for Mourinho with Bailly having been a revelation since his arrival from Villarreal in the summer of 2016.
However, the United boss has backed his side to cope without the centre-back ahead of coming busy run of fixtures which will start with a Sunday's trip to West Brom.
"But now we have [Phil] Jones back and we have [Chris] Smalling, even [Daley] Blind, so it's a position we have good cover in but of course we'll miss the player."
Mourinho also confirmed United have no new injuries to face West Brom but the club website suggests that Marcos Rojo and Marouane Fellaini will remain on the sidelines due to their respective head and knee injuries.
Rojo already missed the midweek victory over Bournemouth after having a clash with David Silva during the recent defeat to Manchester City.
Meanwhile, the Belgium international is yet to play a game since the victory over Brighton on 25 November.
The United boss could thus be without five first-team players to face West Brom as long-term casualty Michael Carrick and suspended Paul Pogba are also expected to miss the game, with the Frenchman serving the final match of his suspension.
The remaining of the players should be available but Mourinho suggested that he will make some changes in his line-up from the team who beat Bournemouth on Wednesday [13 December] night.
"A bit of recovering, a bit of rotation," he said. "I'll change a few players from match to match because I think it is almost impossible for players to play all these matches in December and the beginning of January."