Adam Hadwin is the clubhouse leader at 6-under 66 on Thursday as the Workday Charity Open kicked off at Dublin, Ohio.
Hadwin carded seven birdies and one bogey in a strong round at Muirfield Village Golf Club.
The Canadian bogeyed his first hole -- the par-4, No. 10 -- before later finding his stride. He birdied five of his last eight holes, including draining an 18-foot putt on No. 9 to end his round.
"Just hitting good shots, quality shots to the right side of the hole, giving myself looks," Hadwin told reporters of his round. "I hit some really good iron shots there starting on 18 kind of through four and five, and then made a couple good putts there on seven and nine to finish the round."
Collin Morikawa, who is still on the course, was making a strong run at holding the first-round lead.
Zach Johnson, Canada's Nick Taylor and Japan's Hideki Matsuyama were tied for third after completing their rounds at 5 under.
Taylor's round rated as a surprise as he is playing for the first time since the coronavirus pandemic halted play in March. He had three birdies and an eagle on the par-5, No. 11.
"I didn't have a lot of expectations," Taylor said after his round. "I've played a lot of golf the last month, month and a half, so I felt ready in the sense of playing, in that playing mode."
Justin Thomas, Pat Perez, South Africa's Louis Oosthuizen and New Zealand's Tim Wilkinson were in the clubhouse at 4-under 68.
Among the golfers to shoot 3 under were Xander Schauffele and Australian's Jason Day.
Spain's Jon Rahm had a bumpy day while finishing at even-par 72. The World No. 2 player had five birdies but also had three bogeys and a double-bogey 6 on No. 6.
World No. 6 Brooks Koepka shot 74 while struggling badly over his first nine holes. Koepka had three bogeys and a double-bogey on 18 before recovering with three birdies on his latter nine holes.
--Field Level Media