Manchester United interim boss Ralf Rangnick has insisted that he cannot force any injured players to play for the club.

The German was responding to comments questioning the absence of a number of players ahead of United's 4-1 defeat to rivals Manchester City on Sunday.

Cristiano Ronaldo was reportedly ruled out after suffering a hip flexor injury on Friday, whilst fellow striker Edinson Cavani was missing for a sixth consecutive game.

However, speaking on Sky Sports, Roy Keane questioned the injury to Ronaldo: "We talk about Ronaldo being a machine and very rarely getting injured... it doesn't add up to me."

Rangnick quashed those claims following the defeat though: "I have to believe my medical department. My doctor came to see me on Friday morning before training and told me Cristiano Ronaldo cannot train because of some problems with his hip flexor and the same was true on Saturday and that's why he couldn't be part of the squad.

"It's just a fact, if players tell the doctor and the medical department that they are injured and cannot play. I have to accept it as a manager.

"I cannot force a player to play if he thinks he's not available because he has an injury."

Despite impressing for parts of the first half at the Etihad Stadium, the Red Devils went in at half time 2-1 behind, before a sluggish second-half performance saw United slump to a heavy 4-1 loss to City.