In ordinary circumstances the missing of an opening hole, 6ft putt by a tournament leader would deliver hope to the field. But these are extraordinary times, where such aberrations by Brooks Koepka make no difference. When Koepka slipped up again, from inside 3ft at the 9th, his lead was a mere seven shots.

Koepka will begin the fourth round of the 101st US PGA Championship at 12 under par and holding a seven-stroke advantage. Hope among all others is publicly forlorn and privately non-existent. Barring a delivery of kryptonite to Bethpage, or someone placing explodable balls in his golf bag overnight, Koepka will win his fourth major in eight attempts.

A Saturday 70 meant Koepka ended the round with precisely the same margin for error he had started with. Jazz Janewattananond, Harold Varner III, Luke List and Dustin Johnson are tied at the summit of the tournament within the tournament. At least the chase for second will be fierce.

Koepka’s domination of this event is such that comparisons with Tiger Woods are inevitable. The 15-times major winner himself drew parallels before leaving Bethpage with a missed cut on his CV. Woods, in his all-conquering prime, led fields a similarly merry dance in golf’s biggest tournaments. Koepka routinely gives the impression of not being altogether bothered about perceptions of him but his status is now such that he has to be considered in elite company in golfing history.

The Bethpage galleries watch on as Brooks Koepka chips on to the 18th green during his third round at the PGA Championship. Photograph: Julio Cortez/AP

Some may argue a consequence of the Floridian’s display here has been a relatively dull major. They did not say that when Woods blitzed the opposition. The difference is that Woods’s artistry – and recurring wizardly – contrasts with Koepka’s functional style. The sight of thousands of spectators heading for Bethpage’s exit with the leader still in the early stages of his back nine was telling. He does not seem to be the captivating viewing that Woods once was. Either that, or the galleries regarded this as a foregone conclusion.

Six years ago Koepka was winning the Montecchia Open on the Challenge Tour. In the event of what must be inevitable glory on Sunday he will move inside the PGA Tour’s top 50 of all-time money winners. Ricky Elliott, Koepka’s caddie, will need the services of an investment banker before long.

Koepka’s short work in Long Island continued within five third-round holes, by which time he had birdied twice. That uncharacteristic slip at the 9th was followed by another bogey at the 10th after Koepka found rough from the tee. This was Koepka’s first dropping of successive shots since March. The response arrived at the 13th but was handed back to the course on the 16th. Koepka’s level-par 70 was easily his “worst” performance of the week.

The rest of the leaderboard is wonderfully compact. Johnson needed to get up and down from thick rough alongside a greenside bunker at the 18th to secure a Sunday tee time with Koepka, his close friend. Johnson fluffed his attempt to get to the green, with a bogey ensuing.

Quick Guide USPGA Championship leaderboard - third round Show USPGA Championship leaderboard - third round 1 Brooks Koepka (USA) -12

T2 Dustin Johnson (USA) -5

T2 Luke List (USA) -5

T2 Jazz Janewattananond (THA) -5

T2 Harold Varner III (USA) -5

T6 Matt Wallace (ENG) -4

T6 Hideki Matsuyama (JPN) -4

T8 Adam Scott (AUS) -3

T8 Xander Schauffele (USA) -3

T8 Patrick Cantlay (USA) -3

T8 Jordan Spieth (USA) -3

Janewattananond, playing in his first US PGA, signed for a 67 to move to minus five. The charismatic Thai’s backstory is terrific; he adopted his nickname due to his father’s love of jazz music and spent two weeks living as a monk in 2016. “I arrived here on Monday, it was raining,” he said. “Tuesday was raining. The course plays so tough because the rough was so long, the ball didn’t go anywhere. I was having a nightmare, thinking, ‘How am I going to play this golf course? I’m not going to break 80.’ This has exceeded my expectations. People keep shouting ‘We love you.’ They love me here.” Varner III matched Janewattananond’s aggregate courtesy of a 67 of his own. List held second place at one Saturday stage but had to settle for a 69 and a place in the five-under quartet.

Matt Wallace and Hideki Matsuyama sit at four under. Jordan Spieth headed in the wrong direction on moving day, his 72 meaning he is nine adrift of Koepka. Spieth’s poor Saturday scoring is beginning to look like more than a coincidence.

Tommy Fleetwood’s 72 slid him back to even par. Justin Rose is alongside Fleetwood after a 73 which included two sixes on par-fives and a double-bogey five at the 14th.

Rory McIlroy looked disconsolate after a 69 which moved him to two over par and still outside the top 20. The Northern Irishman insisted, though, that he harboured no inherent sense that he should be competing at the summit of the leaderboard.

“No, because I feel that would be very entitled,” McIlroy said. “I haven’t played well enough to be out there and that’s the way it is.”

If McIlroy harbours professional jealousy towards Koepka, who should match his major haul of four on Sunday evening, he hides it well. “It’s awesome, it’s so good,” said McIlroy of Koepka’s performance.

“It’s great to watch. He’s definitely, in these events, playing on a different level than almost anyone else.” Almost? This felt like the understatement of the year.