Kyle Stanley was the early clubhouse leader on the opening day of the WGC-Bridgestone Invitational after producing a seven-under-par 63 but he had a high-quality chasing pack breathing down his neck at Firestone Country Club.
Beginning his round at the tenth tee, American Stanley notched six birdies in his first nine holes to reach the turn in 29 as the early starters made the most of favourable scoring conditions.
Stanley then carded two further birdies and a single bogey on his back nine to post the lowest first-round score at this event since 2012.
Patrick Cantlay was alone in second place after mixing seven birdies with one bogey in his 64, with Rory McIlroy among the large group another stroke further back on five under after his flawless 65.
Australian duo Jason Day and Marc Leishman, Indian Anirban Lahiri and America's Luke List were alongside McIlroy in a tie for third, while afternoon starters Ian Poulter and Rickie Fowler were also on five under as they made their way down the stretch.
Course-specialist Tiger Woods - an eight-time winner at Firestone - opened with a 66 to sit a shot further back, as did Englishman Matthew Fitzpatrick and US Open Champion Brooks Koepka.
Stanley, who finished in a tie for fifth at the WGC - Dell Technologies Match Play earlier in the year, opened his birdie account at the 11th - his second - from six feet before making back-to-back gains at the 13th and 14th.
Overall I'm really happy with the day - Kyle Stanley
The 30 year old then reeled off three straight birdies from the long 16th, including a brilliant 17-foot putt at the 18th, to climb to six under.
After picking up another shot from close range at the long second, Stanley carded his only bogey of the day at the fourth but bounced back straight away with a birdie on the short fifth to return to seven under.
And Stanley safely parred his remaining four holes to take the early clubhouse lead.
"The course is pretty soft right now, the fairways and the greens are pretty receptive," said Stanley.
"But, you know, I feel like it suits my game pretty well for a guy that hits a lot of fairways and a lot of greens.
"I took last week off so came in here pretty well rested and the putter feels good as well.
"So overall I'm really happy with the day."
