Ralf Rangnick has rubbished Roy Keane's claim that Cristiano Ronaldo's injury that ruled him out of the Manchester derby "doesn't add up."
The Portugal star was missing from Manchester United's damaging 4-1 defeat by Pep Guardiola's men due to a hip problem.
Rangnick provided an update on Ronaldo's condition before kick-off revealing he couldn't train on Friday and wasn't able to travel with the squad to the Etihad, as a result.
He said: "Cristiano (Ronaldo) had some problems with his hip flexor on Friday and since then, he didn't train."
Anthony Elanga came into the side to face Manchester City instead but Keane was not convinced with Ronaldo's diagnosis given the fact "the man is a machine who is rarely injured."
HAVE YOUR SAY! What do you make of Roy Keane's remarks on Cristiano Ronaldo's injury? Comment below.
He told Sky Sports: "The surprise is Ronaldo with the problem with his hip flexor, but United have a bit of pace they still have to come out and play with pride and quality.
"Elanga is a good player, positive and is an intelligent player.
"There seems to be something more with the Ronaldo situation, the manager coming out talking about something about his hip flexor but the man is a machine and is rarely injured, but every now and again he comes out with that about his hip flexor, doesn’t add up to me."
But Rangnick has dismissed any notion of illegitimacy over Ronaldo's injury as he directly responded to the former United midfielder's claim.
"I have to believe my medical department," the Red Devils interim boss explained.
"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."
Veteran striker Edinson Cavani was also ruled out of the game despite training the last three days as Rangnick expressed his frustration at the Uruguay international's unavailability.
Rangnick added: "Edi trained well in the last three days but, in the end, he didn't feel quite well enough to be able to play.
"What does it help if I tell you it's frustrating? 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."
Asked if Cavani decides when he plays, Rangnick continued: "Edi trained in the last three days, he trained well, but he still felt after those three training sessions that he is still not fit to play.
"This is a fact and as a manager, I cannot force a player to play if he doesn't feel fit or well enough to play.
"I cannot force a player to play if he thinks he's not available because he has an injury."
Raphael Varane and Luke Shaw were also missing as the pair tested positive for COVID during the week.
