Rory McIlroy declared the Saudi Arabia-backed breakaway Super Golf League "dead in the water" as he accused Phil Mickelson of making "selfish, egotistical, ignorant" remarks.
A number of high-profile players are said to have been targeted by organisers of the lucrative proposal, including Dustin Johnson and Bryson DeChambeau.
But the most prominent names to have discussed the league publicly – including Rory McIlroy, Jon Rahm and Collin Morikawa – had pledged allegiance to the PGA Tour, and Johnson and DeChambeau joined them on Sunday, a significant turn of events.
Mickelson recently gave a remarkable interview to the Fire Pit Collective's Alan Shipnuck, in which the six-time major champion claimed he and several other golfers paid their lawyers to construct the proposed breakaway competition's operating agreement.
As Mickelson put it, the motivation was "a once-in-a-lifetime opportunity to reshape how the PGA Tour operates", claiming Saudi money had provided "leverage" for negotiations.
Mickelson criticised PGA Tour commissioner Jay Monahan, and McIlroy, speaking on Sunday after tying for 10th place at the Genesis Invitational, made clear his disdain for the 51-year-old's comments.
"I don't want to kick someone while he's down obviously, but I thought they were naive, selfish, egotistical, ignorant, a lot of words to describe that interaction he had with Shipnuck," McIlroy said.
"It was just very surprising, disappointing, sad, and I'm sure he's sitting at home sort of rethinking his position and where he goes from here."
DeChambeau declared his commitment to the PGA Tour, stating: "While there has been a lot of speculation surrounding my support for another tour, I want to make it very clear that as long as the best players in the world are playing the PGA Tour, so will I."
Johnson also spoke out, saying: "Over the past several months, there has been a great deal of speculation about an alternative tour, much of which seems to have included me and my future in professional golf. I feel it is now time to put such speculation to rest. I am fully committed to the PGA Tour."
Asked if such players supporting the US-based PGA Tour would finish off the Super Golf League venture, McIlroy said: "Yeah, yeah. I mean, who's left? Who's left to go? There's no-one. It's dead in the water in my opinion. I just can't see any reason why anyone would go."
Four-time major winner McIlroy added: "I've always reiterated that I feel like this is the best place to play golf if you're an elite professional golfer."
He praised tour executives and welcomed the comments from DeChambeau and Johnson.
"I was really glad to see DJ and Bryson fill out those statements this week," McIlroy said. "We all want to play against the best players in the world, and they are certainly two of the best players in the world. It's nice to know that they're committed to playing here and committed to making this the best tour in the world."