The American world number nine, who won his maiden major last year at Erin Hills, shot a five-over-par 75 at a brutal and extremely windy Shinnecock Hills that left him six shots behind clubhouse leaders Ian Poulter and Scott Piercy.

“Obviously, it’s really tough. The wind’s blowing about as hard as it can,” said Koepka. “The pin locations are pretty tough.”

“Sometimes you’re having to aim outside the fairway. If the wind’s off to the left, you’re aiming outside into the left rough, and if you just pull it and turn it with the wind, you’re into the left rough.”

Koepka’s day started in fine fashion as he made birdie at the par-four first, but that was the only highlight of a round that also included two double-bogeys and a pair of bogeys.

When Koepka captured last year’s US Open, he did so on a course that was plundered by the field and criticised by many onlookers as being too easy, especially for a tournament that is meant to be the toughest test in golf.

Koepka’s 16-under total of 272 last year matched the US Open to-par scoring record set by Rory McIlroy in 2011.

But it was a different story at Shinnecock Hills, where the winds and treacherous greens made many of the world’s best golfers struggle.

Koepka was playing in a group with two-time US Masters winner Bubba Watson (77) and former PGA Championship winner Jason Day (79), whose combined score was 21-over-par 231.

Yet despite the rough start, Koepka said his group had not lost hope, given the unpredictability of a US Open.

“I don’t think any of us really got frustrated. I think everybody was just trying to grind it out,” said Koepka.

“You know, it’s a US Open. You can shoot, whatever, five over today and shoot one under tomorrow and be just fine going into the weekend. So I’m not too concerned,” said Koepka.

“I mean, it is tough. I would have liked to have those two three-putts back, and I would have taken that and felt I’d played okay.”