Man Utd boss Ole Gunnar Solskjaer challenges Jose Mourinho's key signings to step up amid injury crisis

Ole Gunnar Solskjaer has laid down the gauntlet to three of Jose Mourinho’s highest profile signings as he contends with the injury crisis gripping Manchester United.

The Norwegian has told Romelu Lukaku, Alexis Sanchez and Fred it’s time to step up in the absence of up to 10 players for Wednesday’s trip to Crystal Palace.

All three have disappointed this season despite arriving with big reputations – but will be required in the absence of key players Marcus Rashford, Anthony Martial, Jesse Lingard, Ander Herrera and Nemanja Matic.

Juan Mata, Phil Jones, Antonio Valencia, Matteo Darmian and Mason Greenwood are also out of game at Selhurst Park – prompting Solskjaer to call up youth players Angel Gomes, Tahith Chong and James Garner.

But he wants United’s big-name players to start producing – particularly £75m Lukaku and highest earner Sanchez.

“It’s a chance for them to play to their potential,” he said. “Reputation is one thing, the potential is high, because the two of them are good mates.

"They link up well together so this might be a chance for them two together to find some form and give us a selection headache for when everyone gets fit again.”

Lukaku has shown signs of finding form in recent weeks after admitting he had bulked up too much during the summer.

The Belgian is still working on a programme to lose the extra muscle put, but Solskjaer remains confident he can get the forward back to his best.

“We ask our forwards, strikers to work at a higher intensity, to run in behind, but that’s what he likes, so I’m sure he’ll be fine,” said the interim manager. “Muscle is not so difficult to get rid of. He’s lean, but he’s muscly. We’ll get him in the box and score us goals, that’ll be his job.”

Getting a response from Fred could be more difficult.

The £52m summer signing hasn’t featured in any of United’s last nine matches and has been a peripheral figure all season, despite being a target for Pep Guardiola last January.

Solskjaer delivered a blunt message to the midfielder ahead of what could be his first Premier League start since Boxing Day.

Asked how he could get more opportunities, he said: “Play well when he gets a chance, keep training, keep working. We’ve had a midfield three of Herrera, (Paul) Pogba and Matic, and they’ve done really well together.

“It’s not like we’ve been really bogged down with too many games. That why we’ve kept them three together. I’m sure that Fred, when he gets the chance, he will grab the opportunity.”

Solskjaer accepts United’s spate of injuries could be linked to the higher intensity he’s demanding from the players since taking over from Jose Mourinho. But he’s warned them there will be no let up.

He admitted: “It’s probably linked, yes because when do you make that change? Do you wait until pre-season and think you will change results by just not asking them to run?

“Or do we start now and show them what the demands of intensity and how we want to play?

“You have seen what I have chosen, I have chosen we need to play as a Man United team and if you want to be a part of Man United, it’s a survival of the fittest.”