Rangnick confirmed Ronaldo, who did not travel with the
United squad to the Etihad Stadium, was ruled out of the 187th Manchester derby
with an injury to his hip flexor.
Roy Keane questioned the veracity of Ronaldo's injury before
kick-off, saying: "We talk about Ronaldo being a machine and very rarely
getting injured… it doesn't add up to me."
Ronaldo's sister, Katia Aveiro, also appeared to question
the 37-year-old's absence before the match by liking an Instagram post claiming
he is not injured and was dropped by Rangnick.
Speaking after the United's chastening 4-1 defeat to City,
Rangnick responded to Keane's claims.
"I have to believe my medical department," the
United 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."
Rangnick, who deployed Bruno Fernandes and Paul Pogba in a
false-nine position in Ronaldo's absence, also faced questioning over the
availability of striker Edinson Cavani.
The Uruguay international was missing for the sixth
successive game, with Rangnick voicing his frustrations pre-match after being
informed by the player he did not feel he could play. In his absence United
delivered a toothless attacking display, failing to register a single effort in
the second half.
"What does it help if I tell you it's
frustrating?" Rangnick added. "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."
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."
Defeat - United's second under Rangnick and first away from
home since Ole Gunnar Solskjaer's final game as manager at Watford - saw City
restore their six-point lead at the top of the Premier League, thanks to
doubles from Kevin De Bruyne and Riyad Mahrez.
The chasm between the champions and their cross-city rivals
stands at 22 points. The scale of task United have in bridging that gap was not
lost on Rangnick, although he refused to be drawn on the precise areas where
improvements are needed.
"The second half showed that if they [City] have
momentum, and are 3-1 up, that it's almost impossible to keep them away from
your own goal, at least for our team," he added.
"Look, I'm still the manager of this team for another
10 games in the Premier League and hopefully a few more games in the Champions
League.
"It doesn't make sense now to start speculation about
how many players would we need and in what positions, this is my issue. Right
now it's about preparing the team for the Tottenham game and after that, for a
very important game against Atletico in the Champions League.
"Right now, I am happy with the players we have, this
is clear. For us it is important to look ahead, to develop the team, which we
have in the last couple of weeks and months.
"We don't always play against Manchester City, we have
shown are capable to win other games. This is my major job in the next two and
a half months."
City's emphatic, dominant victory was the perfect response
to Liverpool cutting their lead at the top to three points with victory over
West Ham.
Pep Guardiola hailed the performance as one of the best of
his tenure, and called for more of the same as the champions bid to repel the
best opponent the Spaniard has faced during his managerial career.
"In the first half we struggled to get going, but we
felt from the first minute of the second half that we had the game in our
hands," Pep Guardiola said.
"I'm so demanding, but I know my players' limits. If
the second half wasn't our best level then I don't know what we have to do.
"The biggest success for this team is to have is to be
there again to fight the best opponents I have ever faced in my life in
Liverpool."