Americans have had a stranglehold on the PGA Championship for seven years, but if they can't keep that streak going next week, no US man will be a reigning major golf champion.
Should an American not lift the crown at Oak Hill, international golfers will have four consecutive major triumphs and for the first time in a decade, American golfers will hold no major men's titles.
Since the Saudi-backed breakaway LIV Golf League lured away top PGA Tour talent and began play last June, global players have ruled the majors.
Spain's Jon Rahm won last month's Masters, Australian Cam Smith took the 2022 British Open before jumping to LIV weeks later and England's Matthew Fitzpatrick captured last year's US Open.
The last time Americans were without a reigning major champion was in 2013 after South Africa's Ernie Els captured the 2012 British Open, Northern Ireland's Rory McIlroy claimed the 2012 PGA, Aussie Adam Scott won the 2013 Masters and England's Justin Rose took the 2013 US Open.
The seven-year PGA Championship win streak, the longest US title run at the event since the 1980s, began with Jimmy Walker in 2016 and includes Justin Thomas in 2017 and 2022, Brooks Koepka in 2018 and 2019, Collin Morikawa in 2021 and Phil Mickelson in 2022.
World No 1 Rahm became the first European to win both a Masters and a US Open. A triumph at Oak Hill would put him halfway to a calendar-year slam and only a Claret Jug shy of a career Grand Slam.
"It would be great," Rahm said. "To be able to finish it out and close out and do a Grand Slam would be absolutely amazing."
Rahm has won a record $14.5 million this season in PGA prize money, breaking 2022 Masters winner Scottie Scheffler's old mark of $14 million.
"Feeling good with the game is at right now," Rahm said. "I'm glad to be in good form this year."
World No 3 McIlroy, a four-time major winner, has taken a mental health break since missing the Masters cut, taking 47th at Quail Hollow in his lone Oak Hill tuneup.
"It has been a taxing 12 months mentally," McIlroy said. "More for my mental and emotional well being I needed to be at home for those few weeks.
"I'm in a better head space."
Second-ranked Scheffler expects a difficult test on an unfamiliar layout.
"I've never played Oak Hill," he said. "I know it's a great golf course. I've heard it's very challenging."
Three-time major winner Jordan Spieth, who needs only the PGA Championship to complete a career Slam, is questionable with a left wrist injury.
"I'm focused on healing as quickly as possible," 10th-ranked Spieth said.
Six of eight PGA Championship winners from 2009-2017 were first-time major champions, the last of them being Thomas
Thomas added a second PGA Championship title to his resume when he beat Will Zalatoris in a playoff last year. Since then, however, Thomas has only three top-five finishes in 19 PGA starts.
"I'm making some moves in the right direction," Thomas said. "Seems like basically every round I'm playing I shoot the highest score I possibly can. I'm just trying to stay the course and stay patient."
MAJOR WIN FOR LIV?
Three of the top six at the Masters were from LIV Golf, whose players are banned from PGA Tour events and will only face such rivals in majors.
No player has won a major while a LIV Golf member but 18 LIV players seek that breakthrough at Oak Hill. That includes seven players with a combined 17 major titles, among them Smith and this year's Masters runners-up Mickelson and Koepka.
Six-time major winner Mickelson returns after winning the 2021 PGA at 50, becoming the oldest major champion. He skipped last year ahead of his jump to LIV.
"I'm going to give myself quite a few chances in some upcoming majors because my game is coming around," Mickelson said.
"I've kept myself in good shape, I've been fairly injury free and I'm able to work the necessary amount to play at a high level."
Four-time major winner Koepka says 54-hole LIV events offer a fine chance to prepare for majors.
"Just trying to make sure I tune everything up," Koepka said. "I live for the majors and that's where I'm trying to perform."