(Reuters) - Justin Thomas turned on the jets mid-round and opened a three-stroke lead after the third round at the WGC-Bridgestone Invitational in Akron, Ohio on Saturday.
A week before defending his title at the PGA Championship, Thomas carded three-under-par 67 after starting the day tied for the lead with Englishmen Ian Poulter and Tommy Fleetwood.
The American gathered five birdies in nine holes from the sixth en route to a 14-under 196 total with one round left at Firestone Country Club.
Northern Irishman Rory McIlroy also had a 67 to jump into second place with Poulter (70) at 11-under. Australian Jason Day is another shot back after a 69.
Fleetwood got an unlucky break at the first hole when his approach shot hit the flagstick and clattered off the green, which set the tone for a miserable day.
He carded 74 and plunged seven strokes behind.
Tiger Woods, an eight-times champion at Firestone, battled to a 73 and fell 11 strokes behind.
Woods dismissed speculation that his surgically-repaired back had bothered him.
"I'm fine," he said. "I just played like crap."
Asked to specify, he said: "Everything. I didn't warm up very well, didn't hit the ball crisp or clean.
"Very similar to the first day. Difference is I made everything the first day. Today I didn't make anything."
McIlroy was more satisfied after wielding his best weapon, the driver, more than 300 yards with monotonous regularity.
"I like to hit driver as much as possible and this course allows me to do that," he said.
"It allows you to be aggressive off the tee. (Hitting) nine out of 14 fairways today is a good number if I can do that tomorrow hopefully I'll have a chance."
(Reporting by Andrew Both in Cary, North Carolina, editing by Pritha Sarkar)