The pair are close friends, with the Juventus forward congratulating Nurmagomedov after his successful lightweight title defence over Justin Gaethje and subsequent retirement at UFC 254.
Nurmagomedov is currently in Dubai as he prepares to corner his cousin Umar for his UFC debut against Sergey Morozov on the undercard of Conor McGregor's rematch with Dustin Poirier at UFC 257.
And Makachev posted a clip of Nurmagomedov chatting to Ronaldo on FaceTime, quipping "Damn, he's putting together a serious team" after Khabib had earlier met Dutch legend Clarence Seedorf.
Ronaldo is a fan of combat sports and recently spoke about meeting boxer Anthony Joshua back in 2019.
Speaking to boxing star and current IBF and IBO middleweight champion Gennady Golovkin as part of DAZN's Parallel Worlds, Ronaldo revealed: "We had the opportunity to speak last year in Dubai, I was with Joshua and we had conversation.
"Thirty-three years old is that age where you start to feel down. I don’t wanna be in the sport, in football, where people say, ‘Cristiano was an unbelievable player and now he’s slow’.
"I don’t want that. You can take care a lot of your body, the body’s not a problem I don’t think. It’s here [points to his head], your motivation, experience. I think this is the most tough.
“In sport, you can gain maturity. Look at [Roger] Federer in tennis; he’s 37 or 38 years old, and he’s still at his peak, and there are some in boxing too.
"Between watching a football match or a boxing or UFC fight, I choose boxing or UFC. I don’t think I could have been a boxer, it’s tough. You have to be born for that, with that gift."