Los Angeles - Americans Kelly Kraft, JT Poston and Derek Fathauer shared the first-round lead at Colonial on Thursday with a host of big names on their heels in the PGA Tour Dean & DeLuca Invitational.
Kraft, Poston and Fathauer fired five-under par 65s on the par-70 Colonial Country Club layout in Fort Worth, Texas.
They were one in front of Northern Ireland's Graeme McDowell, rising Spanish star Jon Rahm and American Scott Brown, with five-time major winner Phil Mickelson heading a group a further stroke back on 67.
McDowell, the 2010 US Open champion, is making his debut in a tournament that clashes with the European PGA Championship at Wentworth and made the most of benign morning conditions to grab four birdies without a bogey.
"It's a real classic old-school golf course," he told PGATour.com. "At the back of your mind you're hoping you making right decisions off tees and get the right strategy on holes. I really felt like I played the course correctly today. Nice to get a low score under my belt."
Mickelson also teed off early and finished with three straight birdies at the seventh, eighth and ninth.
"We got a nice break because it was pretty calm this
morning and we had an opportunity to get it going early," said Mickelson,
a two-time winner at Colonial who rolled in a 30-footer to cap his round.
"The course challenges you tee-to-green but once you get it on the green you really have an opportunity to take advantage of the shots you hit in there, as opposed to some courses we play that are overly contoured."
Fathauer set an early target with six birdies in his 65 - including four in his final nine holes.
Kraft, runner-up at Pebble Beach this year, had five birdies without a bogey, his 40-footer at 16 giving him a share of the lead.
Poston had six birdies against one bogey.
Brown had seven birdies and held the outright lead at six-under before a double-bogey at the 18th dropped him into a tie with McDowell and Rahm.
Mickelson was joined on 67 by another two-time winner in Zach Johnson along with Ryan Moore, Kevin Kisner, Nick Watney and Sean O'Hair.
Defending champion Jordan Spieth endured a roller-coaster of a day in which four bogeys and a double-bogey and six birdies - including back-to-back birdies to end his round - yielded an even-par 70.
Leading scores after Thursday's first round of the PGA Tour's Dean & DeLuca Invitational at Colonial Country Club in Fort Worth, Texas (par-70, USA unless noted):
65 - Derek Fathauer, JT Poston, Kelly Kraft
66 - Scott Brown, Graeme McDowell (NIR), Jon Rahm (ESP)
67- Ryan Moore, Kevin Kisner, Nick Watney, Phil Mickelson, Sean O'Hair, Zach Johnson
68 - Kevin Streelman, Kim Whee (KOR), Scott Piercy, Stewart Cink, Vaughn Taylor, Kang Sung (KOR), Michael Thompson, Michael Kim, Webb Simpson, Kevin Tway, Curtis Luck (AUS)