A trademark late rally ensured Jordan Spieth kept his bid to become the youngest player to complete a career grand slam on track in the 99th US PGA Championship.
Spieth’s dramatic Open victory at Royal Birkdale means another at Quail Hollow would see him join Gene Sarazen, Ben Hogan, Gary Player, Jack Nicklaus and Tiger Woods in having won all four majors.
But the 24-year-old had to recover from three over par with three holes to play to card an opening 72 and lie five shots off the lead held by Denmark’s Thorbjorn Olesen.
Among the Irish Padraig Harrington faces a near impossible task to make the cut, starting tomorrow on 8-over par.
A good day for Shane Lowry could see him make the weekend, however. He tees off tomorrow from 3-over after a 74 today.
Two-time US PGA winner Rory McIlroy was among the later starters and reached the 13th 1 under par.
Fellow Ulster man Graeme McDowell was 1 over after 10.
US Open champion Brooks Koepka was a shot off the lead along with fellow Americans Grayson Murray, Gary Woodland and Chris Stroud, with England’s Paul Casey another shot back on two under.
Starting on the back nine alongside fellow 2017 major winners Koepka and Sergio Garcia, Spieth opened with five pars before carding his first birdie on the par-five 15th, only to promptly give the shot back on the next after finding two bunkers.
Spieth also bogeyed the first, one of the new holes constructed at Quail Hollow immediately after it hosted last year’s Wells Fargo Championship, after failing to get up and down from a greenside bunker.
And when he three-putted the fifth and sixth from just off the green, the world number two was in danger of seeing his title challenge ruined on the opening day.
However, birdies on the next two holes - courtesy of what Spieth described as a "phenomenal" hybrid into the par-five seventh and a "fantastic" wedge to the eighth - repaired most of the damage.
"Historically I’m pretty solid with the lead so that was kind of the goal," Spieth said. "It’s much easier when you are on the front page of the leaderboard than it is coming from behind.
"Given it’s the first round I know I’m still in it, but I know that tomorrow’s round becomes that much more important to work my way and stay in it. I’ve got to make up ground.
"If I’m five back at the start of the day, I’ve got to be less than five back after Friday to really feel like I can play the way this golf course needs to be played and still be able to win.
"I drove the ball well today. If you told me I was going to hit my driver the way that I did today, I would have definitely thought I shot a few under par. I can’t putt any worse than I did today."
Spieth had insisted on Wednesday that he had no "burning desire" to surpass Woods as the youngest grand slam winner and was "freerolling" this week, but added: "I don’t think I was as freerolling as I thought I would be, as you can tell by some frustration.
"If I would have shot one over and didn’t strike it well and everything was average, it would have been fine. But when I had the chances that I had and I just couldn’t get the ball to go in on the greens, that is when I get the most frustrated I can get out there."
Olesen had only played 13 majors before this week, but was ninth in the Open in 2012 and finished sixth on his Masters debut the following year.
The 27-year-old was also 10th in last week’s WGC-Bridgestone Invitational and carried on where he left off on Sunday with a round containing six birdies and two bogeys.
"I feel like the last two months I’ve been playing very well without really getting any results," Olesen said. "Last week I was struggling a bit the first two days with my driving but then I sorted that out over the weekend and started making a lot of birdies there.
"I’ve had a couple of top 10s in majors and I feel like I’ve learned a lot over the years. I feel like I’m better prepared to be in contention over the weekend and have a chance to win.
"I feel more confident with myself and my game than I probably did a few years ago. I just have to stay relaxed the next few days, still trying to keep the ball in the fairway, and then I know I can hit it close and make some birdies."