Roy Keane insists it is a "dangerous conversation" to suggest Manchester United are a better team without Cristiano Ronaldo.
United manager Ralf Rangnick revealed the Portuguese superstar was unavailable for his side's trip to the Etihad to face fierce rivals Manchester City on Sunday.
The German declared that the 37-year-old sustained a hip flexor injury on Friday and wasn't able to train ahead of the Manchester derby, thus forcing him to miss the crucial clash.
However, former Red Devils captain Keane, who earlier claimed something "doesn't add up" with regards to Ronaldo's absence, fired a warning to those insisting United are a better team without the five-time Ballon d'Or winner.
Speaking on Sky Sports, Keane declared: "I think it’s a dangerous conversation when you’re talking about ‘it’s good Ronaldo is not available’ or whatever the reasons are - whether he’s injured or whatever.
"I still think you’d want Ronaldo in your team.
"Of course, with counter-attack the most important thing is the pace, but to say that it might be a plus that Ronaldo isn’t available, I don’t accept that."
The Irishman was embroiled in a heated exchange with fellow Sky Sports pundit Jamie Carragher earlier in the campaign after the former Liverpool defender questioned United's decision to re-sign Ronaldo.
Carragher has claimed on countless seasons that the striker is a "passenger" and is one of many critics who have questioned Ronaldo's work-rate and compatibility with United's current crop.
The prolific Portuguese forward has experienced a mixed season since making a sensational Old Trafford return on deadline day, from Juventus last summer.
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Despite notching 15 goals in 31 appearances across all competitions for United this term, Ronaldo has cut a frustrated figure at times and recent endured his longest goal drought since 2010.
Ahead of Sunday's Manchester derby, Gary Neville was another insisting Ronaldo's absence could play into United's hands given their intentions to play on the counter - a ploy which has seen the Red Devils victorious in their last three Etihad visits.
“Manchester United will be playing on the counter," Neville told Sky Sports ahead of the match.
"United over the last three or four seasons - particularly under Ole - were a counter attacking team, really comfortable sitting back and punching out through Rashford and others on the break. That will be exactly the same today.
“Cristiano not being in the team, I can’t say it’s a negative, but it’s not the big loss that it could be in other games because on the counter-attack they need to be dangerous today and they are better off with Rashford counter attacking than Ronaldo.”
While Keane fired a warning over the notion that United are better off without Ronaldo, he also questioned the legitimacy of Rangnick's injury claims, insisting something "doesn't add up".
"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," Keane admitted.
"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.
"Every now and again he comes out with that about his hip flexor - it doesn’t add up to me."
