DeChambeau's 423-yard bomb came on the 470-yard first hole Thursday at Muirfield Village Golf Club. He pulled out his driver and laced the 191-mph shot over three bunkers before the ball landed in the fairway, about 46 yards short of the hole.
DeChambeau chipped his second shot 2 yards from the hole before he sank a 6-foot shot for birdie. He ended the day at 1-over par and tied for 42nd place.
Tony Finau had the first-round lead with a 6-under 66 in Dublin. Ryan Palmer shot a 67 for a second-place finish in the first round. Gary Woodland, Brendan Steele, Jon Rahm, Lucas Glover and Charles Howell III also are in the top-five.
The second round of the Memorial Tournament teed off Friday morning. DeChambeau tees off with Colin Morikawa and Patrick Cantlay at 1:06 p.m. EDT. Tiger Woods -- who is tied for 18th -- teed off at 8:17 a.m.
The four-day tournament ends Sunday. The winner will earn $1.6 million.