Fort Worth - American Dustin Johnson fired a bogey-free five-under par 65 on Thursday to claim the first-round lead at the USPGA Tour's $6.4 million Colonial tournament.
Johnson, who has already collected one victory this season, at the WGC-HSBC Champions in October, hit 16 of 18 greens in regulation and nabbed five birdies to take a one-stroke lead over New Zealand's Tim Wilkinson and Americans Hunter Mahan, Harris English and Robert Streb.
Mahan was on fire on the front nine at Colonial Country Club, making the turn at six-under, thanks in part to his eagle-birdie start.
But he couldn't keep the momentum, and ended his round with a double-bogey at 18 to join the group on four-under 66.
Wilkinson, making his first start at Colonial, played without a bogey.
Three-time winner this season Jimmy Walker was among a group of 10 players tied for sixth at three-under 67.
Walker was joined by Jason Dufner, Jordan Spieth, Tim Clark, Brice Garnett, Freddie Jacobson, Bo Van Pelt, Ken Duke, David Hearn and Wes Roach.
Defending champ Boo Weekley posted a one-over par 71 and is in a large group of players tied for 64th that also included Australian Adam Scott.
Scott is playing for the first time since taking over the world number one ranking from Tiger Woods on Monday.
The 2013 Masters winner teed off on 10 and endured a tough opening nine holes, but managed to turn it around with three birdies coming in.
"It is a testing golf course," said Scott, who had four bogeys in his first nine holes. "I just had to be a little patient.
"Sometimes on a course like this, you need to be. Even with a short iron or wedge in your hand you can't force it because bogeys are easy to come by."
Scott bogeyed his second hole, the par-five 11th, after he needed two strokes to get out of a fairway bunker. He added bogeys at the 15th, 17th and 18th before he stopped the bleeding with a two-putt birdie at the par-five first. He made a three-footer for birdie at the second, and picked up one more stroke at his penultimate hole, the par-three eighth.
He said he didn't feel any extra pressure to live up to the number one ranking, although the regular nerves were there on the opening tee.
"I managed to tighten up on the back and make a couple of putts," he said.
65 - Dustin Johnson
66 - Tim Wilkinson, (NZL), Hunter Mahan, Harris English, Robert Streb
67 - Tim Clark (RSA), Freddie Jacobson (SWE), David Hearn (CAN), Jason Dufner, Jimmy Walker, Ken Duke, Bo Van Pelt, Brice Garnett, Jordan Spieth, Wes Roach
68 - Robert Allenby (AUS), Vijay Singh (FIJ),
Aaron Baddeley (AUS), Brian Davis (ENG), Ricky Barnes, George McNeill,
Josh Teater, Kevin Chappell