Britain's Paul Casey fired an eight-under par 62, matching the lowest round of his career, to seize a four-stroke lead after Saturday's third round of the US PGA Travelers Championship.
The 40-year-old Englishman, aided by some swing advice from coach Peter Kostis, seeks his third career US PGA title and second of the year after his bogey-free weekend start at TPC River Highland in Cromwell, Connecticut.
Casey hit all 18 greens in regulation for just the third time in his career to stand on 16-under 194 for 54 holes with American Russell Henley second on 198.
Casey had complained of pulling the ball off the tee but a lesson with Kostis at the driving range saw him improve his posture and adjust his stance closer to the ball to produce the low round of the tournament.
"That's something I rarely see, 18 greens in regulation, so whatever he told me worked," Casey said.
Casey, a 13-time European Tour winner, hadn't won anywhere since 2014 until capturing March's US PGA Valspar Championship, edging Tiger Woods and soon-to-be Masters champion Patrick Reed by a stroke.
Casey had back-to-back birdies at the second and third holes and two more in a row to close the front nine, a nine-footer at the par-3 eighth and a 20-footer at the ninth.
After a tap-in birdie at the par-5 13th, Casey drove the green at 15 and made a 23-foot eagle putt to jump ahead by three strokes at 15-under.
"Hit a real neat 3-wood in there," said Casey of his approach. "I was in between clubs. Couldn't afford to be short so I went with the 3-wood."
At 18, Casey dropped his approach three feet from the cup and tapped in for birdie and a four-stroke edge.
India's Anirban Lahiri shared third on 199 after a third-round 65 with Americans J.B. Holmes and Brian Harman.
Australia's Jason Day shot 66 to stand in a pack on 200 with Americans Bubba Watson, Ryan Blaum, Beau Hossler and Bryson DeChambeau.
"I put a little bit more pressure on my short game to step up," Day said. "It has been a pretty good week with the short game. I'm chipping really nice."
The Aussie holds out hope of threatening Casey on Sunday.
"If you get away 2-under on the front side tomorrow and can get something going from 11 on, 13, 15 and one out of the last three, that's where you can start pushing," Day said. "You can put a lot of pressure on the guys in front."
Watson has won the event twice, once from six strokes back in the final round. He's chasing Casey too but admits it's a long climb.
"I've got to play a solid round," Watson said. "I have to be around 10-under to give him a scare."
American James Hahn aced the 158-yard, par-3 11th hole with an 8-iron on his way to a 67 to stand on 204.
Casey hit all 18 greens in regulation for just the third time in his career to stand on 16-under 194 for 54 holes