Stewart Cink, rejuvenated by his selection for the US Ryder Cup team in Ireland next month, charged one stroke clear at the WGC-Bridgestone Invitational on Saturday.
One of two wildcard picks selected by US captain Tom Lehman, the 2004 champion fired a six-under-par 64 to overhaul tournament favourite Tiger Woods in the third round at Firestone Country Club.
"It was a very good day," Cink told reporters after finishing at nine-under 201.
"I played well all the way and, when I made mistakes, I was able to save pars. On this golf course, it's so tough. It feels very much like a major out there.
"It's tougher than last week," the 33-year-old added, referring to the PGA Championship at Medinah outside Chicago.
"The fairways are harder to hit, the greens are faster and the greens are more firm. This week, if you don't hit it solid, it's probably going over (the green). You need to spin the ball."
Although Woods surrendered his overnight lead with a run of four bogeys before finishing in a tie for second place, Cink expects the world number one to rally in Sunday's final round.
"With him, it's only a matter of time until he gets back on the birdie streak again, I'm sure," he said.
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However, Cink conceded he was taken aback by Woods's initial slide down the third-round leaderboard.
"I was a little surprised because it's Tiger Woods and the way he's playing lately," he added. "But the way the course is anybody, even the great Tiger Woods, can make some bogeys out there."
Cink's 64 was the only bogey-free round of the day, and reflected his more relaxed approach to the game after being selected on Monday for his third Ryder Cup team. "That sense of relief is evident with me, Davis (Love III), Lucas (Glover), all the guys that were border line or pressing hard to make the team," he said.