Louis van Gaal has criticised Marcos Rojo for neglecting to tell him he was hurt as Manchester United have been plunged into a defensive injury crisis.
The Dutchman said he will have to name Phil Jones, who is not fit and is yet to play this season, on the bench against Ipswich on Wednesday because three other defenders have been ruled out.
Argentina international Rojo made his first start of the season in Sunday's 3-2 win at Southampton as he took over from Luke Shaw, who broke his leg against PSV Eindhoven last week, at left-back.
But the former Sporting Lisbon player had a hamstring problem and did not inform Van Gaal or the club's medical department.
Now he may have to use first-choice centre-back Daley Blind at left-back against Ipswich in the Capital One Cup or pick Ashley Young or Matteo Darmian out of position.
"First we have to see who is available," Van Gaal told MUTV. "Luke Shaw is of course not available, but Marcos Rojo is not ready to play. Neither is Paddy McNair, who is also injured.
"I thought we were right on time for Rojo because we changed him in the game and he didn't warn us that he was injured. He has a hamstring injury and McNair has a minor injury.
"It's not so nice that we have three defenders injured but I can line up eleven players so that is not the problem.
"But I have to admit that because of the injury of defenders, I shall have Jones on the bench but he is not fit.
"Maybe he can play 30 minutes. He is a lucky boy that I don't have other substitutes."
Jones suffered from thrombosis in the summer but three of United's five centre-backs -- in the Englishman, McNair and Rojo -- are unable to start so if Blind operates at left-back, Michael Carrick may have to drop into defence.
Van Gaal is yet to disclose if Rojo will be fit for Saturday's home game against Sunderland or the Champions League clash with Wolfsburg next week.