Brandt Snedeker shot an eight-under-par 63 to take the lead at the end of the opening day of the BMW Championship in Illinois.
The American reeled off seven straight birdies during his blemish-free round to fashion a one-shot advantage over compatriot Zach Johnson.
Snedeker won the FedEx Cup play-offs last year and looks to have chosen the penultimate event of this season's four-tournament series to launch another tilt at the lucrative prize.
Tiger Woods is one of four players tied for third place on five under, former Masters winner Charl Schwartzel, Steve Stricker and Kevin Streelman also carding rounds of 66 on Thursday.
"It was one of those days where everything seemed to go right in the middle of the round," Snedeker said.
"I got off to kind of a slow start and made a great birdie from off the green on 13 that got everything moving in the right direction. To roll off seven birdies in a row kind of came out of nowhere. I wasn't expecting it."
Englishman Luke Donald and Northern Ireland's Graeme McDowell were the leading British players after both shot opening rounds of 70 to finish one under.
However, Rory McIlroy and Lee Westwood had nightmare days carding rounds of 78 and 80 respectively.