The hamstring injury suffered by Anthony Martial before Manchester United's win on Thursday is "not heavy," manager Louis van Gaal says.
Martial pulled up in the warm-up for United's Europa League last-32 second leg against Midtjylland.
The France international was replaced up front by 18-year-old debutant Marcus Rashford, who scored two crucial goals to help United rally for a 5-1 win.
After the game, Van Gaal praised Martial for admitting that he did not feel fit to play.
"The first impression is that it [the injury] is not heavy," Van Gaal said. "He is tired and he can be tired because he is 20 and he has played all the matches. What is remarkable is that he stepped down himself."
Martial's withdrawal meant that United had suffered injuries in the warm-ups of both legs against Midtjylland. Goalkeeper David De Gea sustained his knee injury during the prematch period in Denmark.
They have contributed to an alarming injury list for United, all over the pitch, which was reflected by their team selection against Midtjylland at Old Trafford.
Stand-in captain Michael Carrick featured at centre-back, with Chris Smalling's shoulder injury having depleted their options before the game.
Speaking about the latest injury blow to Martial, Van Gaal said: "I couldn't believe it was happening again. It is unbelievable. It is difficult to change or rotate when you don't have any other players.
"I don't think Martial has a muscle injury because he stepped down when he felt his hamstring was tight.
"It is ridiculous to lose two players in the warm-up against the same opposition, but we had to keep going and we did."