The Northern Irishman was aggrieved by the behaviour of Joe LaCava, Cantlay’s caddie, who appeared to encroach into McIlroy’s space on the putting green and then waved his cap in close proximity to the four-time major winner as he prepared to line up a putt to halve the match.
The argument continued in to the car park at the Marco Simone Golf and Country Club, with Europe teammate Shane Lowry having to intervene and usher McIlroy away.
Revealing that he used to be on friendly terms with LaCava during his time caddying for good friend Tiger Woods, McIlroy has suggested that Cantlay has been a bad influence on his bag carrier.
“Here’s what angered me,” McIlroy explained to the Irish Independent. “My relationship with Cantlay is average at best. We don’t have a ton in common and see the world quite differently.
“But when I saw he was getting stick on the 17th and 18th greens, I tried to quiet the crowd for him. And I don’t think Fitz [Matt Fitzpatrick, his partner] and I were afforded the same opportunity to try and hole those putts to halve the match.
“I shook Joe’s hand, and Patrick’s hand. Those three putts he made on 16, 17 and 18 were fantastic, and under that pressure, to give your team a glimmer of hope going into Sunday was big balls. So all respect to him.
“There was a bit of argy-bargy at the back of the 18th green with Fred Couples and Thomas Bjorn – and that’s fine – but as I’m walking back to the locker room I can feel this red mist coming over me. ‘No! That wasn’t right.’
“And they’re trying to defuse the situation, but I start having a go at them. Joe LaCava used to be a nice guy when he was caddying for Tiger, and now he’s caddying for that d*** [Cantlay] he’s turned into an a***.
“I still wasn’t in a great headspace.”
McIlroy also revealed that Woods had reached out in the aftermath of the incident to check he was ok.
The pair are business partners on a new golfing venture, TGL, which is due to launch in January.
“There were also three texts and two missed calls from Tiger, because they’re obviously still close,” McIlroy said. “I sent him a quick message: ‘It will be fine – long day – just want to go to bed.’”
Europe regained the Ryder Cup with victory in Rome, continuing their dominance on home soil.
The United States have not won the biennial event away from home since the 1993 edition.