Bryce Molder opened with a six-under 64 to take a one-shot lead at the Dean & DeLuca Invitational.
The American finished strongly at the Colonial Country Club on Thursday, with six birdies on his back nine - including four straight to finish - lifting him into the lead.
Molder had produced pars on each of his first nine holes before birdies on holes one and two got him going.
"I hit a lot of greens early, 20-30 feet and just kind of rolled up close," he told PGA Tour Radio.
"Then, all of a sudden, I hit a couple close when I made the turn on number one and two, got some close birdies and I've always loved these greens.
"I got some good looks late and they happened to go in."
At six under, Molder is a shot clear of countrymen Patrick Reed and Webb Simpson, along with India's Anirban Lahiri.
Reed started on the back nine and finished with six birdies, while Simpson's only blemish came at the par-three fourth.
Jason Dufner, Ryan Palmer, Kyle Reifers and Martin Piller are a shot further back.
World number two Jordan Spieth made a solid, albeit unspectacular start, to the PGA Tour event.
The two-time major champion had four birdies to go with a bogey, which came when he found the bunker off the tee at the fourth.
Defending champion Chris Kirk opened with an even-par 70 to be tied for 45th.