William McGirt carded a six-under-par 64 to take a three-shot lead at the WGC-Bridgestone Invitational on Thursday.
McGirt is followed by world number one Jason Day, Jimmy Walker and Emiliano Grillo as the trio fired three-under-par 67s.
India’s Anirban Lahiri sits in a tie for fifth with world number two Jordan Spieth, Rickie Fowler and Charley Hoffman on two-under.
Meanwhile, defending champion Shane Lowry struggled on Thursday and is in a tie for 51st after recording a six-over 76.
McGirt began his round with an 18-foot birdie putt at the third before going on to make a 28-foot putt at the fifth and a 27-foot putt at the sixth. Another birdie followed at the eighth to round off a brilliant front nine. The 37-year-old continued to excel on the back nine as he made two more birdies to complete a bogey-free round.
“He did not.”
What a finish for William McGirt. Drains long par putt for 6-under 64. https://t.co/E4yTgrSXCV
— PGA TOUR (@PGATOUR) 30 June 2016
Day got off to a mediocre start as he made two birdies and a bogey on the front nine. The Australian turned his fortunes around on the back nine though as he made two birdies to remain in a good position heading into the second round.
Spieth, who carded a 68, had a front nine to forget, shooting bogeys at the fourth and seventh. The American started the back nine with a birdie at the 11th and another bogey at the 12th before stepping up his game and finishing off his round with four consecutive birdies from the 15th to 18th, which included a fantastic 25-foot putt at the 17th.
Fowler enjoyed a lot of success on the front nine even after overcoming a bogey at the first. Following that hiccup, he went on to make four birdies, which included a 26-foot chip from the rough at the fourth. The world number seven was unable to maintain his momentum though as he made a lone bogey on the back nine.
Meanwhile, Lowry struggled to mount any sort of challenge on Thursday as his round of 76 consisted of a birdie and seven bogeys.