David Lingmerth and Jason Dufner opened with impressive seven-under 65s to take the first-round lead at the Memorial Tournament.
Lingmerth, the 2015 champion at Muirfield Village, had a mixed round that included eight birdies, an eagle and three bogeys on Thursday.
The Swede shares the lead with Dufner, who was far more consistent and made just one bogey.
Jordan Spieth, fresh from a runner-up finish at the Dean & DeLuca Invitational, continued his return to form, while Dustin Johnson had a forgettable round.
American world number six Spieth carded a six-under 66 to be tied for third with countryman Daniel Summerhays.
Spieth, who had missed consecutive cuts before last week, made bogeys at 17 and 18 to finish his front nine, but responded in style.
He holed five birdies on his back nine, including a 17-foot putt at the par-four sixth.
Johnson, the world number one, made 15 pars but had a triple-bogey and double-bogey as he shot a 78.
Justin Thomas and Lucas Glover sit at five under, a shot ahead of An Byeong-hun and Sam Saunders, as 34 players went under par in the opening round.
Rickie Fowler was among them, salvaging a two-under 70 after making a poor start with a triple-bogey seven at the second.
Included in his recovery was a birdie at 18, where he holed out from the bunker.
World number three Jason Day struggled, needing two late birdies to shoot a three-over 75.
Defending champion William McGirt made a solid start with a 71 leaving him tied for 26th.