Chad Ramey made a splash on his Players Championship debut as he emerged as the surprise clubhouse leader on Thursday at Ponte Vedra Beach.
World No.1 Jon Rahm was seven shots back while Rory McIlroy carded a four-over 76.
Ramey, who missed the cut in his last three PGA Tour starts and is 225th in the world rankings, went out early and carded a bogey-free eight-under-par 64 at TPC Sawgrass that left him one shot clear of two-time major champion Collin Morikawa.
Canadian Taylor Pendrith and American Ben Griffin were a further shot adrift while Justin Suh was five under through 15 holes when play was suspended due to darkness.
Ramey, who won his lone PGA Tour title last year in Punta Cana, appeared calm throughout a round in which he birdied four of the first seven holes and added four more on the back nine.
"Not easy at all. I might have made it look that way but it wasn't easy at all," Ramey told reporters after matching his low round of the season. "It was fun, first time to shoot a score on such an iconic course like this. You can't ask for any more."
Morikawa was cruising along at three under before an eagle at the par-five second, his 11th hole, where his approach shot from 235 yards settled three feet from the cup.
Morikawa, who missed the cut last week at Bay Hill, added another two birdies to grab the outright lead in the PGA Tour's flagship event before Ramey overtook him with two late birdies.
While few would be surprised to see Morikawa near the top of the leaderboard, many onlookers expected those in the mix to have come from the heavyweight group featuring Rahm, world No.2 Scottie Scheffler and No.3 McIlroy.
The trio, who have traded top spot in the world rankings this year, were the pre-tournament favourites but experienced mixed fortunes.
Rahm, who has three wins this year, carded his lone bogey on his penultimate hole and shot a one-under-par 71 that left him three back of Masters champion Scheffler, who birdied three of his final four holes for a solid 68.
"You don't have a lot of margin to miss out here," said Rahm. "Even when you're in the fairway, you have to hit a lot of quality shots to give yourself a birdie chance."
It was a different story for McIlroy, however, as he began his day with a double-bogey at the par-four 10th where he missed the green with his approach, sent his third shot into a bunker and failed to get up and down.
The four-times major winner, runner-up last week at Bay Hill, responded immediately with a birdie but struggled to find his rhythm and found himself repeatedly playing from the rough.
Last year's champion Australian Cameron Smith is not in the 144-player field along with five of the top-10 finishers from the 2022 Players Championship as those who joined LIV Golf are banned from competing on the PGA Tour.
Min Woo Lee (68) is tied sixth and Australia's leading contender.
One behind him is Cam Davis, followed by Harrison Endycott and Jason Day (both 70), Adam Scott (72), Aaron Baddeley (73) and Lucas Herbert (82).
