They spend a lot of time together on the course, in the gym and at home, so Koepka has seen that U.S. Open trophy plenty at Johnson's house in South Florida.
Koepka, 27, shot a 5-under 67 in the final round and finished 16-under to tie the U.S. Open record set by Rory McIlroy in 2011.
Yet Koepka revealed that his decision to launch his career in Europe, far from the support structure of family and friends in the United States, had nearly become unbearable. "And I got hot with the putter", Koepka said.
The first Major golf tournament in Wisconsin has produced a first-time major champion. Having missed out at PGA Tour qualifying school in 2012, he went to Europe, where he quickly won three times on the European Challenge Tour, the continent's second tier. I would have had to play some pretty spectacular golf to catch him. It's probably unlike anything I've ever played in the states.
His friends and professional support team preached patience and pleaded with him to focus less on obsessing about victories and avoid getting down on himself.
"And I felt like I really stayed patient all week".
HARMAN: I finished last at Memorial two weeks ago, so who knows.
HARMAN: I think it should. I just stayed in the moment.
Koepka earned $2.16 million, the largest single-day earnings in golf.
After two years of U.S. Open calamity, the USGA enjoyed a controversy-free week. His message was short and sweet. "It was, like, two minutes", Koepka said.
His play this past fall in the Ryder Cup when the US whipped Europe, where he said he had never felt more pressure, helped him immensely. Matsuyama birdied No. 18 to close within one shot of Koepka with five holes to play, but Koepka turned on the afterburners late Sunday.
"It made me feel a lot better seeing Brooks shoot 5-under", Thomas said. "And that's what we've been working on, but maybe a day like today is all it needed to just kind of calm down".
"He's a great player and he's a great gentleman". Somebody who's got a long career.
"That was kind of the changing point of the round for me", he said.
"I played really well today", said Matsuyama, who watched Koepka close out his title on a TV in the clubhouse.
"I love this golf course, obviously, but I thought it was a great test", Koepka said. "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".
HARMAN: No, I don't think there's - I think most of the good players don't really compare themselves to their peers.
Brooks Koepka made it sound simple, this winning of the 117th U.S. Open golf tournament Sunday at Erin Hills.
Rain on Wednesday and overnight Friday kept the greens slow, and subdued winds for the first three days allowed much of the field to score below par.
He said he wasn't aware that he was a birdie away from the record. "I'm sure someone even heard me say that". "It would have been nice. But it's still a pretty cool accomplishment". I wouldn't want to play with the opposite wind because there would be some holes that would be a bit stupid.
Asked if he plans to continue playing major championships on the regular tour, Stricker said, "As long as I can get in them, I'll play them".
Their scores - 13-under, 12-under, 11-under, and a trio of 10-under's - would have won every U.S. Open contested, save three. He's not anxious about the low scores the first few rounds.
In the history of the championship, from 1895 to 2016, six players total reached double-digits under par in the championship. McIlroy and Tiger Woods (12 under at Pebble Beach in 2000) had been the only players to finish there.
Koepka entered Sunday in a three-way tie and a shot behind 54-hole leader Brian Harman.
Players are on the course for the final round of the U.S. Open in blustery conditions at Erin Hills.
Dana Fry beamed as he stood on the range Sunday morning while Hideki Matsuyama and others warmed up for their final rounds at the U.S. Open.
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Flowers and missing persons posters were taped to the gates of the church, while bags of donations were piled outside the door. An additional public inquiry set up by the government will determine if building regulations had been broken.
French Open 2017 men's review: Day nine
I didn't feel like today I was playing slower than I was in the other matches. 'I think he's probably a bit less confident. The 30-year-old has won eight of their 10 previous meetings, most recently at the ATP World Tour Finals last November.
Brroks Koepka wins US Open title
After a poor shot on the par-3 13th, Koepka made a long putt to save par and keep him one stroke ahead of Matsuyama in the lead. Open clubhouse leader, though at five under par Steve Stricker eventually finished 11 strokes behind victor Brooks Koepka .
Koepka claims first major title by taming Erin Hills
He closed with a 5-under 67, only realizing after his par on the final hole that a birdie would have set yet another U.S. Koepka said the world number one had called him on Saturday, offering some advice which came in handy.