At the par-5 10th hole, his first of the day, Koepka failed to convert a 4-footer for birdie and had to settle for an opening par.
"Easier holes, " he said of Nos.
"I thought to myself: 'They are not giving birdies at all".
"I know people who work for the Trump organisation who joke with me, "You're the only one who has got a cheque from the President". Casey was 3-under through five holes before stalling.
The PGA Championship venue has three completely new holes, 18 re-grassed greens and dozens of more subtle changes from the course that previous year hosted a PGA Tour event.
Every player on the PGA Tour has a way of getting ready in the days leading up to a major. I'll watch all nine innings and however long it goes and people are just, really.
After a almost 10-minute wait at the 223-yard, par-3 17, Herman's tee shot failed to clear the front bunker by a hair.
"Tee to green it was pretty solid", Spieth said.
"The disappointing thing was we got put on the clock when we were a hole ahead of the group behind us and that's when my round started to go..." he rued, speaking to RTÉ Sport shortly after signing his card. "And I seriously feel I can do that". But this weekend at Quail Hollow will be Spieth's only shot at becoming the youngest player to ever do it. Tiger Woods was about six months older than Spieth is now when Tiger completed his own career grand slam at age 24.
It's not the first time Phelps has shadowed Spieth around the course.
"This is a very, very hard golf course right now", he said of the 7,588 yard host course, lengthened nearly 200 yards from the last time it was used for a PGA Tour event in 2015.
Jason Day continued his steady progress back towards his best form at the PGA Championship of the United States today with a one-under par 70 that has him tied-15. "It's a little disappointing but I brought it back with a couple birdies to at least having a chance going forward". I feel like I've been putting well the whole round.
The star attraction for the afternoon has Rory McIlroy, Jon Rahm and Fowler, and all three have made the turn under par. Instead, he quickly regained his focus and birdied three of the next five holes to get back under par.
Swimmer Michael Phelps, a 23-time Olympic gold medalist who knows a thing or two about performing at his best under crushing pressure, spent Thursday following Spieth around Quail Hollow.
Another three bogeys followed on the front nine before a birdie-birdie-par finish to close on the leaders.
In contrast, defending champion Jimmy Walker slumped to an 81 and Phil Mickelson and Ernie Els struggled to rounds of 79 and 80 respectively in their 100th major appearance.
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