Bubba Watson established an early clubhouse lead as the World Golf Championships-Bridgestone Invitational began in Akron, Ohio.
The American birdied four holes in a row from the 11th in a six under par 64 at Firestone to sit two shots ahead of compatriots Phil Mickelson and Kenny Perry in the clubhouse.
France's Gregory Bourdy and Northern Ireland’s Rory McIlroy were leading the European challenge during the early stages, as they both carded two under par rounds of 68.
"I made three birdies, I just made a mistake on the par three - number 15 - missed my shot," said three-time European Tour winner Bourdy.
"But otherwise it was consistent. I missed just a few putts from nothing, so it was a bit unlucky, but it was good all around. The driver I think was one of the keys here to play well, so I tried to keep that driver on the fairway, all week."
McIlroy was delighted to put himself in contention with a strong opening round.
“I'd love to get my game in the best possible shape going into next week, but I'm focusing on this week and trying to do better than I did last year,” he said.
“I didn't play very well here last year. I feel it is a golf course if I can play well on, it's a course that I can get it going and possibly put myself in with a chance to win.”
McIlroy was playing with Mickelson, who recovered from a poor start in his latest bid to depose Tiger Woods as World Number One.
Mickelson and Lee Westwood both have the chance to end Woods' 270-week reign at the top of the rankings at Firestone this weekend.
Starting on the back nine, World Number Two Mickelson bogeyed the final two of his opening six holes, but he immediately bounced back with a birdie before producing five more after the turn.
“It was a good day in that I got off to a poor start and was a couple over par and then was able to turn it around and shoot 30 on my back nine, which is the front, to get in good position after the first day,” said the Masters Tournament Champion.
