The Northern Irishman again admitted to his dislike of the two-time US Open champion as he launched into a candid rebuke of DeChambeau's behaviour on Friday night amid the drama over the American's two-stroke penalty.
After he'd finished his third round on Saturday, McIlroy was asked about DeChambeau's battle over the penalty imposed by rules officials for him inadvertently improving his backswing path by trampling some high grass.
The delay, as DeChambeau went out on to the course with officials and tried to clear his name, ended up delaying the publication of the third-round tee-times until around 11pm and prompted criticism from a number of players, with England's Marco Penge calling it "a joke".
McIlroy's enmity with DeChambeau is well known, with the Masters champion having refused to speak with his rival when they played together during the final round of his 2025 win at Augusta which brought him the career grand slam.
"Late night for everyone," sighed McIlroy, when asked about the rules controversy.
"I won't pretend to be up here and defend Bryson. I'm not particularly fond of him. I think a lot of it is performative. I think a lot of it's for attention.
"To hold the tournament hostage like that, and to have all of us, players, volunteers, everyone waiting on him to depart, I didn't feel like it was a great look.
"I was watching it live. I was up in the players' lounge watching it with a few other players and as soon as he made the step into the ball, we all sort of looked at each other, and we were like, 'that didn't seem right'.
"Then when I heard that he was called in by the rules officials, it was pretty obvious for why.
"I think there's no doubt that he improved the line of his backswing. Whether it was careless or whether it was intentional, I don't think it matters.
"Hopefully, it was careless, but I think the two-shot penalty was justified for sure."
Meanwhile, McIlroy's struggles on the greens continued to haunt him on Saturday as the six-time major winner ended with a one-under 69 that leaves him two under for the tournament and makes him believe he's more or less out of the title picture.
"It was a little scrappy in areas. I feel like I could have probably shot 67 or 66 and if I'm three back of Foxy (the then clubhouse leader Ryan Fox on eight under) going into tomorrow I feel like I have a legitimate chance," said McIlroy.
"But I'm three back of that. I probably feel like I'm a little too far behind.
"Never say never. If I go out tomorrow and get to double digits, you never know, but I certainly am not going out tomorrow thinking like I've got a great chance to win."
