Fiftieth-ranked Brian Harman of the United States, who was the 54-hole leader, duelled with Koepka into the back nine before finishing 12-under, tied for second place with Japan's Hideki Matsuyama, ranked fourth in the world. Koepka's 16-under tied Rory McIlroy for the lowest score in relation to par in US Open history, and Koepka is just the third US Open victor to finish double digits below par (Tiger Woods).
"It is Father's Day, so hopefully - like I said, I didn't get him a card, so I really hope this works", Koepka said.
While he hit 350-yard drives with his driver and 3-wood, one of his best weapons was patience.
Harman wasn't alone. Rickie Fowler (72) entered a major Sunday with a good shot at victory for the second time since April, but didn't get much going. "I feel comfortable. Being in contention in a major is new and I'm excited", said Thomas. But it was an important 120 seconds.
Johnson's advice was simple: Stay patient, stick to your game and "you will win the thing", Koepka said.
"I just tried to get as low as I could (on each hole) and stay focused", Koepka said.
The golfers had their way with Erin Hills for four days, which is unusual for a U.S. Open, where hard courses and diabolical setups by the USGA traditionally make pars, not birdies, the objective. And he banked $2.16 million.
"I played really solid from the moment we got here on Monday all of the way through today". And I was pretty far off. He held it together, tied with Koepka early in the back nine, before bogeying the 12th and 13th holes. "Came up a little bit short. But Brooks played so well today", Harman said. "I'm sure someone even heard me say that".
So, I think I didn't really understand the beef that it was getting for the low scores. "With all his peers winning that are younger than him, 27's not old, but he thinks he should be winning every week", he said.
Bummer buddies: Roomies Fowler, Thomas fizzle at US Open
Brooks Koepka had a birdie putt on every hole and made three of them to build a one-shot lead after nine holes Sunday in the U.S. Following Koepka in second place was Hideki Matsuyama of Japan and Brian Harman of the United States at 12-under.
Tommy Fleetwood of England finished on fourth at 11-under, while there was a three-way tie for fifth between Xander Schauffele, Bill Haas and Rickie Fowler, who will be disappointed at failing to eventually challenge for the title, after a wonderful opening round looked like being the talented American's chance to break his major duck. Charley Hoffman (71) finished solo eighth at 9 under.
Koepka has just one win on the PGA Tour, but now has five top tens and a win in 14 career major championships as a professional. I was just exhausted of golf. "He's so unflappable, he could nearly do with a little bit of a kick in the ass because sometimes it's like, 'Are you awake yet?' But despite his mean face he's as calm as it gets". He called it one of his best shots of the week. "He might even smile".
Koepka used this power and accuracy to his advantage. Gary Player and I were the only guys predicting over forty years ago this would happen, and everybody laughed us to scorn.
And for the week, there were 140 sub-par rounds recorded - with 122 coming in the first three rounds. Yet another record fell in the third round when Justin Thomas shot 9-under-par 63, the lowest score in relation to par. Surprisingly, that was his only victory until this, his breakthrough at major championship level.
In all there were a record 138 subpar rounds. The cut (1-over) was the same as last week's PGA Tour event, the FedEx St. Jude Classic. I think that win [at Wells Fargo] was big for him.
Through it all Koepka kept his measured swagger on a roll and never got ahead of himself.
Koepka recorded three quick victories on the satellite circuit to make the step up to the European Tour before the Floridian eventually progressed to the US -based PGA Tour. "But he's played so well in the majors, and played great in the Ryder Cup (at Hazeltine)".
"I wasn't thinking anything other than the shot I just had or was about to hit". He'd like to forget the expected 20-minute bus trip to a hotel in Africa that took three hours.
"I did love it". After three days of benign conditions, players woke up to a howling Wisconsin wind.
"To go over there, I think it helped me grow up a little bit and really figure out that, hey, play golf, get it done, and then you can really take this somewhere", said Koepka, who made his first U.S. Ryder Cup team past year.