Manchester United defender Lisandro Martinez is facing an extended spell out with injury.
Martinez has aggravated a foot injury he suffered in April at the end of last season.
The club says he played with the injury in the defeats against Brighton and Bayern Munich after the setback occurred in the loss at Arsenal on September 3.
Next steps are being considered as assessments continue, the statement added.
Man Utd will also be without Sergio Reguilon for Saturday's visit of Crystal Palace in the Premier League due to a minor injury.
Manager Erik ten Hag has contended with a raft of injury issues in the early stages of this season, but now has Mason Mount, Sofyan Amrabat, Raphael Varane and Harry Maguire fit and available.
Martinez's injury means Maguire, Victor Lindelof or Jonny Evans will fill in against Palace on Saturday and for the foreseeable future as United cope without Martinez.
Reguilon, who was brought in on loan from Tottenham as emergency left-back cover for injured pair Luke Shaw and Tyrell Malacia, was covered by Amrabat in Wednesday's 3-0 win over Palace in the Carabao Cup third round.
Amrabat played as an inverted full-back in United's first meeting with Palace this week, impressing on his Old Trafford debut.
Diogo Dalot, United's only remaining fit recognised full-back, can be used on the left but with Aaron Wan-Bissaka still out Ten Hag has run out of options for cover.Read on m.allfootballapp.com