Canadian Adam Hadwin leads the Memorial Tournament after the first round with world number one Scottie Scheffler and US PGA Championship winner Xander Schauffele just behind.
Seamus Power, meanwhile, fares best of the Irish trio and sits inside the top-10 on three under par.
Leader Hadwin shot a six-under-par 66, with eight birdies and two bogeys, including one on the last hole, while Scheffler lagged one shot behind with six birdies and a bogey.
Schauffele sits a shot behind Scheffler, tied in third place with Sweden's Ludvig Aberg, Canadian Corey Connors and American Collin Morikawa.
The world number two said his putting kept him on the right end of the leaderboard.
"When the ball was in the air, I closed my eyes," Schauffele said. "I wouldn’t call myself religious, but I was hoping that thing was going to be OK.
"If I didn’t make some of the putts I needed to today, it would have been like a two over probably, or worse."
Power lies tied-seventh after carding an opening 69 at Muirfield Village. The Waterford golfer, who qualified for the US Open at the Columbus tournament earlier this week, birdied three of the final five holes to reach three under, part of a quintet which also comprised of Viktor Hovland, Tommy Fleetwood, Akshay Bhatia and Billy Horschel.
Rory McIlroy had an up and down day, saving his round one score with four birdies on the last six holes after hitting two bogeys and a costly double-bogey on the 12th hole, finishing four shots from the lead.
Shane Lowry had a more difficult opening day, dropping three strokes on his inward nine en route to a two-over-par 74.
