Anthony Martial has suffered another injury setback with Ole Gunnar Solskjaer confirming that the Frenchman is struggling with a muscle problem.
Martial was left out of the United squad to face Club Brugge in the Europa League on Thursday night with January arrival Odion Ighalo replacing him up front.
Solskjaer revealed the reason for the 24-year-old's exclusion in an interview before the game.
"He didn't feel right after the training yesterday, or [rather] he walked off during training and he's injured," Solskjaer told MUTV (via the Express).
"So hopefully it won't be too bad but I don't really know yet how long he'll be [out for]."
It is the latest in a long line of fitness issues for the forward. Martial missed a significant portion of this season with a hamstring complaint while he has also suffered from groin and thigh problems in the past.
United's attacking options have already be severely weakened by the injuries of Marcus Rashford and Paul Pogba.
The Red Devils have received criticism for the way they managed the Rashford's fitness problems with reports stating that he was asked to play through excruciating pain. The England international requires surgery on his ankle and is also nursing a double stress fracture in his back, and is not expected to return for at least another month.
Pogba on the other hand could return to training in the coming days as he continues to recover from an ankle operation.
United are entering a crucial stage of the season and will want Martial back to full fitness as soon as possible. Solskjaer's side are engaged in a nail biting race for Champions League qualification and face rivals in this regard, Everton, on Sunday.
They then take on Derby in the FA Cup in a game that will see Wayne Rooney face his former employers.