The former Chelsea star joins the growing list of injured players at Old Trafford as Jose Mourinho's side enter a crucial stage of the season
Reports suggest the Spain international could miss the rest of the season, though United have not confirmed how long his recovery is likely to take.
But his injury means he joins a growing list of absentees as United head into a crucial stage of the season.
Chris Smalling, Phil Jones and Paul Pogba have all picked up injuries in recent weeks while Wayne Rooney remains a fitness doubt.
Zlatan Ibrahimovic and Ander Herrera are also suspended for Saturday's clash with West Brom, leaving Mourinho with a number of selection dilemmas.
The Red Devils face a busy final two months of the season with 11 Premier League matches still to play in their battle to finish in the top four while they remain in the Europa League.