(Reuters) - While former world number ones Jordan Spieth and Rory McIlroy made erratic starts, long-hitting American Dustin Johnson charged into an early two-shot lead at the Memorial Tournament in Dublin, Ohio, on Thursday.
Taking advantage of pristine conditions with a superb all-round game at leafy Muirfield Village, Johnson racked up 10 birdies and two bogeys in the opening round of the prestigious event hosted by Jack Nicklaus.
Johnson briefly got to nine under with four consecutive birdies on his back nine but he bogeyed the par-four 17th after hitting his second shot into a greenside bunker before posting eight-under 64, two ahead of compatriot Hudson Swafford.
Americans Jason Bohn and Kevin Streelman opened with 67s, world number two Spieth carded a 70 and third-ranked McIlroy mixed six birdies with three bogeys and a double to return a 71.
Johnson, a nine-times winner on the PGA Tour whose best finish this season was a third placing at the Houston Open in April, set the tone with an explosive birdie-birdie-birdie start.
"I just played well right out of the gates," Johnson, 31, told reporters. "I hit great shots in the right spot on the greens and rolled in some putts.
"This year, I've felt like I'm playing well. I just haven't quite played up to my potential. With me, it has everything to do with the putter.
"I rolled it well today ... I've been working pretty hard on the putter, and I felt like it's finally starting to pay off."
American Spieth, who clinched his eighth PGA Tour victory at the Colonial tournament on Sunday, relied on his usually brilliant putting to offset an iffy display with his approach shots.
"I felt awesome on the greens," Spieth said after a round that included five birdies and three bogeys. "Just missed a lot of greens. I didn't have great control of the ball today, but I think it's close.
"My putter made up for it for the most part. To shoot one under on my front nine, the back nine, was by far the best that I could have possibly shot. So scoring well."
McIlroy, like Spieth a tournament winner in his most recent start after clinching the European Tour's Irish Open 11 days ago, salvaged an erratic day with a birdie-birdie finish.
"I just needed to try to salvage something out of that round because I felt like I was playing well enough to," said the Northern Irishman.
"I felt like I hit it well enough off the tee to get it close enough to the pins, and most of the time I did that. But I just hit a few loose shots, and that's what cost me today."
Australian world number one Jason Day was among the late starters.
(Reporting by Mark Lamport-Stokes in Los Angeles; Editing by Andrew Both)