Charl Schwartzel bounced back from a late double bogey with a birdie at the last on Thursday to grab a 1-stroke lead at the Memorial Tournament.
Schwartzel finished his opening round at Muirfield Village Golf Club with a 7- under 65.
Scott Piercy sits alone in second place at 6-under, while Josh Teater, Russell Henley, Kyle Stanley and Charlie Wi are tied for third at minus-5.
Bill Haas and Matt Kuchar posted matching 4-under 68s to pace the afternoon wave and share seventh place.
Defending champion Tiger Woods bogeyed his final hole to close out an up-and- down 1-under 71 that included five birdies and four bogeys. He is among a large group of players tied for 27th.
Schwartzel started on the back nine and opened with a par before rolling in a short birdie putt at the 10th.
He bogeyed the 13th to fall back to even par, but then recorded four straight birdies from the 14th, including a 24-foot effort at the 16th, to make the turn at 4-under.
A 14-foot putt at the fourth kickstarted another string of four straight birdies from outside eight feet to move the South African to the top of the leaderboard at minus-8.
Schwartzel tripped to a double bogey at the par-3 eighth after hitting his tee shot into a greenside bunker and blasting his next well past the green to fall into a share of first with Piercy, but recovered with a 13-foot birdie putt at the last to regain the outright advantage.
"The birdie on the last definitely will make my evening a lot better," said Schwartzel. "I felt like I played really well, just ... sort of ticking the ball over and got it to 8-under. Just had a bad one on No. 8, made a double. And that was the very worst I played all day."
Piercy, meanwhile, started on the front nine and reached the turn at 5-under after capping a streak of five consecutive birdies from the fourth by holing a shot from off the green at No. 8.
After trading a birdie at the 11th with a bogey at the 12th, Piercy moved to 7-under with birdies at the 13th and 15th.
But the American chunked his second shot and failed to reach the green at the par-4 18th en route to a bogey, dropping to minus-6.
"I'll take 66 all the time," Piercy said. "It's just learning how to play golf courses. I can hit it over almost all the corners here. But I have to hit a perfect golf shot and if I don't I'm not in a very good spot."
Fourteen-year-old Tianlang Guan continued his impressive season with an even- par 72 in his first round.
NOTES: Schwartzel recorded a round under 70 for just the second time in 21 tries at the Memorial ... Schwartzel has made eight of nine cuts this season. He has also made the cut in each of his five starts at the Memorial ... World No. 2 Rory McIlroy's tripped to a 6-over 78 on Thursday. It was the fifth- highest round of his career and his second-worst at Muirfield Village, following his 79 in the second round last year.