Dublin, United States: Hideki Matsuyama holed out for an eagle at the 17th as he surged into three-way tie for the first-round lead alongside Abraham Ancer and Joaquin Niemann at the Memorial on Thursday.
The trio were tied on seven-under par 65 in the Jack Nicklaus-hosted event at Muirfield Village.
Matsuyama, winner of the event on his debut in 2014, fought back from back-to-back bogeys at the 10th and 11th with a run of four straight birdies starting at the 13th.
He punctuated his blistering run by holing his 136-yard second shot at the par-four 17th for an eagle two.
Five-time Memorial winner Tiger Woods also finished strong, fighting back from four-over through seven holes to post an even par 72.
Woods, who insisted a "stiff" back that bothered him in the early going was nothing to worry about as he continues his comeback from back surgery, birdied three in a row on his inward run.
"I just have days like that," a smiling Woods said of his back. "It's aging and it's surgeries. It is what it is. Just got to make the adjustments. I'm able to make them now.
"At the beginning of the year, I wasn't able to make them, because I didn't really know what to do yet. But now you see me making these adjustments on the fly."
Woods played early, as did Mexico's Ancer and 19-year-old Chilean sensation Niemann, both notching eight birdies with one bogey to reach seven-under.
Niemann is contesting just his fourth PGA Tour event since turning pro immediately after last month's Masters. He finished tied for eighth last week in Fort Worth, a second top-10 finish after his share of sixth in the Texas Open as he tries to use the seven tournament invitations at his disposal to secure his tour status.
"After having played in four tournaments and I have been playing really well," he said. "And after those two top-10s, I have gained a lot of confidence in my game and I'm also feeling better and I feel able to be out here and play good golf.”
American Beau Hossler was alone in fourth on 66 while four others, including former US Open champion Lucas Glover shared fifth on 67.
World number one Justin Thomas and the player he supplanted atop the rankings, Dustin Johnson, were at even par.
Former world number one Rory Mcllroy struggled, sending two balls into the water over his closing five holes in an indifferent two-over par 74.
McIlroy, and coming off a runner-up finish at the BMW PGA at Wentworth, was one-under par standing on the 14th but found water left with his drive and with his second shot down the last.