Dating back to 2019, the two Americans haven’t seen eye to eye and it now seems to have reached a point where, quite frankly, they despise each other.
During this year’s US PGA Championship at Kiawah Island, Koepka was in the middle of a TV interview when DeChambeau said something that clearly irked his compatriot, who rolled his eyes in total and utter disdain.
The pair then continued their spat after DeChambeau had been teamed up with Aaron Rodgers, the Green Bay Packers quarterback, against Phil Mickelson and Tom Brady, another NFL player, in a made-for-TV match that took place last week.
“Sorry bro,” wrote Koepka in a tweet tagging Rodgers, inferring that he’d drawn the short straw, to which US Open champion DeChambeau replied to the four-time major winner through the social media channel: “It’s nice to be living rent free in your head!”
More recently, Koepka responded to reports of fans being elected from the Memorial Tournament on the PGA Tour for yelling his name at DeChambeau by offering free beer to those spectators.
For the first time since the spat started, the pair are on British soil this week for the 149th Open and, in separate press conferences at Royal St George’s, most of the chat was about their strained relationship.
“It was at Liberty,” said Koepka of the fall out having started at the Northern Trust Open, one of the FedEx Cup Play-Off events, in August 2019. “He didn't like that I had mentioned his name in slow play, so we had a conversation in the locker room.
“Then I guess we said something else in the press conference but didn't mention his name in it, and he walked up to Ricky (Elliott, Koepka’s caddie) and said something. It was, ‘you tell your man if he's got something to say, say it to myself’.
“I thought that was ironic because he went straight to Ricky. Ricky told me when I came out, hit a few putts, and then just walked right over to him, we had a conversation. We both agreed we'd leave each other out of it and wouldn't mention each other, just kind of let it die off, wouldn't mention each other's names, just go about it.
“So then he was playing video games online or whatever and brought my name up and said a few things (about Koepka’s physique), so now it’s fair game. Like I said, we had a conversation at Liberty, and he didn't hold up his end of the bargain and I didn't like that, so I'll take my shots.”
A few hours later, DeChambeau was sitting in the same seat as he replied to Koepka by saying: “He can say whatever he wants. I think he said something back at Liberty National about not upholding something.
“I don't know what he's talking about in that regard. Maybe that's on me. Maybe I didn't. I really don't remember anything about that. We just had a conversation that I really don't know what happened, because we haven't really bantered back and forth until now, so it's like why is that happening now.
“If we want to keep bantering back and forth, obviously being respectful and keeping lines where they aren't getting crossed, I think it's fun and a good environment for people in golf.”
The duo will almost certainly be team-mates in the Ryder Cup at Whistling Straits in September. Steve Stricker, the US captain, doesn’t need any infighting as he bids to claim that prize in his home state of Wisconsin.
“You realise it's only a week, right?” replied Koepka to being asked about the biennial event looking on the horizon. “Look, I can put it aside for business. If we're going to be on the same team, I can deal with anybody in the world for a week.
“I'm not playing with him. I'm pretty sure we're not going to be paired together; put it that way. I think it's kind of obvious. It doesn't matter. We're not going to be high fiving and having late-night conversations. I do my thing, he does his thing.
“Yeah, we're on the same team, but it's not an issue at all. I don't view it as an issue. I don't think he does. Like I said, I can put anything aside for a team, business, whatever, just to get the job done. No problem with that.”
And DeChambeau? “Oh, no, not at all,” replied the 2020 US Open champion, who has a new caddie on the bag this week after an on-course bust up with his old one in Detroit a fortnight ago, to being asked if them playing together would be a problem.
“I think it would be kind of funny, actually. I think we'd do well, to be honest. It would create a little interesting vibe for the team or for the guys we're playing against.”
The golfing world can’t wait for the pair to be in the same group, but it will be Saturday at the earliest if that’s going to happen at Sandwich as they’ve been kept apart by the R&A in the opening two rounds.
“Yeah, I would enjoy it,” said four-time major winner Koepka, smiling, of the possibility of that happening in the final group on Sunday in the delayed Claret Jug joust on the Kent coast.
“I'll be close to the final group come Sunday. I always feel like I play well in the big events, the majors. “With everything that's gone on over the last two years, I think there would be a lot of people tuning in.”