Defending champion Jordan Spieth, the world number two trying to become the first player since Curtis Strange in 1988-89 to win back-to-back US Opens, was in a group at one-under with one birdie in his first four holes.

“Had my family here with me, and just kind of kept to myself, went to the locker room, stayed by myself, talked with my caddie a little bit and had my phone off the whole time”. “And to be honest, I was struggling with my swing in practice, couldn’t really work on it [Thursday]”.

Spieth, trying to become the first repeat Open victor since Curtis Strange in 1989, found a positive amid the gloomy conditions. His approach on No. 1 stopped short of the green.

Because of overnight rain that drenched an already soaked Oakmont Country Club, spectator gates did not open until 8 a.m. local time Friday.

Thursday’s opening day of the 116th version of the championship promises to make the week even more taxing.

“I’m playing well though, playing nicely”.

Only seven of the 78 players who teed off in the morning were under par, so even a soft Oakmont presented its share of problems, mostly on the greens.

McIlroy seemed primed for a good showing this week.

Mickelson has been mired in a slump, with no wins since capturing the British Open three years ago. “It hasn’t really sunk in yet”, he said. “It’s the same for everyone”. Bubba Watson was one shot back with four holes to play.

FOWLER’S START: Rickie Fowler opened his U.S. Open with a shot right at the flag on No. 1 that checked up and settled 5 feet away for birdie.

In the gallery nearby a spectator - perhaps speaking for the thousands wondering about the unfamiliar name with the red number next to it - said “I never heard of the guy, but he conquered Oakmont”.

Danny Lee hits from the rough on the second hole. “So it’s difficult. You’ve got to focus hard and do as well as you can”. But it could work against Mickelson, who turned 46 on Thursday, and will have to find the energy to compete with players half his age in what could be the most hard day of golf this year. Matthew Fitzpatrick is level, alongside his fellow Europeans Russell Knox, Martin Kaymer and Shane Lowry. That’s the lowest opening round score in the first round of a major at Oakmont, bettering the 67s put up by Ben Hogan in the 1953 U.S. Open and Tom Watson in the 1978 PGA Championship.

Amateur Scottie Scheffler, a sophomore at the University of Texas, was the leader in the clubhouse at 1 under.

Two holes later, Spieth hit a wedge that checked up about 10 feet short of the hole and then trickled a few inches toward the cup.

Almost three inches of rain fell on the course Thursday, and even greens that are pitched and drain well are bound to be running slower when players get back on the course Friday morning. “But we all know in reality I did give him back his yardage books and he had them”.

“We sat in a cabin for an hour and 10 minutes behind the seventh tee without being given a chance to hit any balls or do anything”.

Play is scheduled to resume Friday at 7:30 a.m., meaning all but the nine golfers who completed the first round can expect to play more than 18 holes.

“I have no idea if we’ll be able to get all 36 in”, said qualifier Tyler Raber, who had been due to tee off in the last group off 10. That means players will return Saturday to finish the second round, after which, the field will be cut to the top 60 and ties.