A trio of 65s earned the early lead as Kelly Kraft, Derek Fathauer and J.T. Poston claimed top spot after the opening round of the Dean & DeLuca Invitational.
Americans Kraft, Fathauer and Poston are a shot clear of the chasing pack at five under to upstage the likes of Sergio Garcia and defending champion Jordan Spieth on Thursday.
Kraft - seeking his maiden PGA Tour title - was flawless on the first day, carding five birdies without dropping a shot at Colonial Country Club.
Fathauer and Poston recorded a bogey each in otherwise perfect rounds in Fort Worth, Texas.
Graeme McDowell was the only player alongside Kraft to go bogey-free on Thursday.
The 2010 U.S. Open winner carded a four-under-par 66 to be level with Scott Brown and Jon Rahm.
A shot further back is five-time major champion Phil Mickelson, who closed out his round with three successive birdies to be within striking distance of the lead.
Ryan Moore, Kevin Kisner, Nick Watney, Sean O'Hair and Zach Johnson are also at three under.
Masters champion Garcia had a one-under-par 69, which included two bogeys and three birdies.
Texas native Spieth opened his title defence with a first-round 70.
Coming off consecutive missed cuts, former world number one and two-time major champion Spieth is tied for 34th heading into the second round.