Sunday's 12 singles matches were already going to be spicy affairs as the USA need a record-breaking comeback from 10.5-5.5 down to win the trophy for the first time on European soil in 30 years.
And there could well be added needle between the two teams following the explosive aftermath of a dramatic and tension-packed win for Cantlay and Wyndham Clark sealed on the 18th green of the Marco Simone course in Rome, the third for the US in the four afternoon fourballs.
Cantlay and Clark prevailed in the day's final fourballs match against McIlroy and Matthew Fitzpatrick, sparking wild celebrations from the US team and fans.
However McIlroy was enraged by the behaviour of Cantlay's caddie Joe LaCava, who was waving his hat and refused to move out of the four-time major winner's way while he was waiting to take a putt which could have halved the hole and match for Europe.
Northern Irishman McIlroy was then filmed having another blazing row with an unidentified member of the USA team in the course carpark, having to be pulled away and bundled into a car by teammate Shane Lowry.
Europe captain Luke Donald told reporters that McIlroy thought "the line was crossed" with LaCava's behaviour, causing a row which dominated headlines following an epic session which ended at nearly 7:00pm local time (18:00 BST).
It was a dramatic third win from four afternoon fourballs for the USA and earned largely thanks to Cantlay, who sunk three crucial putts in the final three holes just as momentum appeared to have definitively swung in the Europeans' favour.
'Ray of light'
The most impressive was at 18, a 30-footer drained under huge pressure which eventually led to McIlroy losing his cool with his American counterparts, who had been trailing by seven points at lunchtime after a dismal effort in the morning foursomes.
"Hopefully have a ray of light and we can build on this session and try and pull off a big victory tomorrow," said Cantlay who competed Saturday without a cap, although he denied the gesture was in protest at players not being paid.
"The hat doesn't fit. It didn't fit at Whistling Straits (when the USA crushed Europe 19-9), and didn't fit this week. Everyone knows that," Cantlay added.
The USA still have a massive task on their hands as no team has ever recovered from more than a four-point deficit at the end of the second day.
That leaves Europe still favourites as they seek the four points needed to claim their seventh straight home win in the Ryder Cup.
Robert MacIntyre and Justin Rose cruised to a three and two victory over Justin Thomas and Jordan Spieth who had come into the tournament with a formidable matchplay record.
Rose had sunk the key 19-foot putt to halve his Friday fourballs match in stunning fashion and on Saturday the English Ryder Cup veteran repeated the trick on the 16th.
"I just knew there was a huge opportunity today," said Rose.
"Obviously nine and 10, we went one up and... I said to Bobby, the next 20 minutes, we have to put our foot down and get out and get a stranglehold on this match. That's exactly what happened."
'Win or die trying'
By that time the USA had already collected two of their afternoon points with convincing wins.
Sam Burns and Collin Morikawa cruised to a 4 and 3 victory over Viktor Hovland and Ludvig Aberg, who ran out of gas after dishing out a record-breaking 9 and 7 foursomes hammering to Scottie Scheffler and Brooks Koepka.
Max Homa and Brian Harman were the only bright spot in the morning foursomes for Johnson's team.
The pair followed that up by prevailing 2 and 1 over Tommy Fleetwood and Nicolai Hojgaard, and Harma has no illusions about their chances on Sunday.
"Backs against the wall. We've got a deep hole to climb out of," admitted Harman.
"But we've got some good players and got a good team. So we're going to fight like hell and either win or die trying."
