MANCHESTER: Wayne Rooney could be thrown into action sooner than planned by Manchester United to solve a growing injury crisis that has left manager Jose Mourinho to warn: "We're in trouble."

Rooney has played just twice in 2 1/2 months due to injury niggles — the latest being an ankle problem — and the fact he has dropped down the pecking order of strikers at United, behind Zlatan Ibrahimovic and Marcus Rashford.

However, Ibrahimovic joined United's injury list on Thursday when he hobbled off with an apparent right knee injury in the Europa League win over Anderlecht. Mourinho, meanwhile, said the 19-year-old Rashford "cannot play every game."

So Rooney could get an unexpectedly quick reprieve, starting perhaps at Burnley in the English Premier League on Sunday.

"He has a good mentality, he is a fighter, he is a strong man, even if he is not in the best condition, even if he is not in the level of sharpness that you need to play high-level football," Mourinho said of Rooney, 31. "But he has the experience and character, so he has to.

"Now we need absolutely everyone."

United will be playing a game every three or four days through to the end of the season because of its involvement in the Europa League and a backlog of fixtures in the Premier League.

Players are playing through knocks, and Mourinho also has a real problem at center back with Marcos Rojo also getting injured on Saturday to likely join fellow defenders Phil Jones and Chris Smalling on the sidelines.

Mourinho's only fit center back is Eric Bailly, although Daley Blind — usually a left back — can move inside and 19-year-old Axel Tuanzebe could also be promoted to the first team.

"We're in trouble. We're in trouble," Mourinho said. "In this moment, Eric Bailly played six matches in a row, and we lost Marcos Rojo, we don't have Jones or Smalling. We are in trouble."