Charl Schwartzel held a one-shot lead at the end of the first round of the Memorial Tournament in Ohio.
The South African made up for hitting a bogey and double-bogey with 10 birdies seeing him to a seven-under-par 65.
It put him a shot ahead of Scott Piercy with a four-way tie for fourth a further shot adrift.
Former world number one Rory McIlroy's miserable run of form showed no sign of abating as he shot an opening-round 78 to finish six over par.
Shane Lowry also struggled in the opening round and matched McIlroy's disappointing round of six over.
McIlroy missed the cut at the BMW PGA Championship last week, and today, starting on the back nine, McIlroy had an ideal first hole with a birdie at the par-four 10th, but it was all downhill from there.
A double-bogey at the 12th heralded a woeful day, with a further three bogeys racked up before the turn.
There was no respite on the front nine as he hit a further three bogeys, interspersed with a birdie at the fifth, before squandering birdies chances at the final two holes.
It was in sharp contrast to the fine play by Schwartzel at the top of the leaderboard.
Schwartzel told pgatour.com: "I felt like I played really well, just ... sort of ticking the ball over and got it to eight under.
"I just had a bad one on number eight, made a double (bogey). And that was the very worst I played all day."
He added on Sky Sports 1: "That was one of the best rounds of the year.
"I hit the ball beautifully.
"I shot it so well. I gave myself so many chances."
However, it was not such a good day for other high-profile names.
World number one Tiger Woods, looking for his sixth victory here, was one of the late starters but he never really got going.
The American hit a bogey on the third and his contribution from then was decidedly mixed with five birdies interspersed with a further three bogeys including one at the last as the American finished with a one-under-par 71.
Piercy hit eight birdies - five of them consecutively on the front nine - only to drop shots at the 12th and 18th.
A further shot behind were Josh Teater, Russell Henley, Charlie Wi and Kyle Stanley with Bill Haas and Matt Kuchar tied for seventh.