Lemont - England's Justin Rose birdied nine holes in an impressive eight-under par 63 on Thursday to seize a two-stroke lead after the first round of the US PGA Tour's BMW Championship.
Rose had eight pars and just one bogey on the par-71 Cog Hill layout and leads Americans Webb Simpson and Mark Wilson in the third event in the US tour's FedEx Cup playoffs.
Simpson won the previous playoff event, the Deutsche Bank Championship, two weeks ago.
South Korea's K.J. Choi was four shots off the lead after a 67.
"Didn't expect that going out there today," said Rose, who hit all 14 fairways and 16 of 18 greens in regulation despite the chilly, difficult conditions.
"I looked to the weather, looked at the temperature, and I thought today was going to be a day to hang in there.
"Little did I know I was about to play so well -- certainly my best round of the year by a long, long way. And could have been top five, top 10 rounds I've ever played for sure."
Rose's 63 was especially impressive on a day that saw only 16 other players break 70. The Englishman's playing partner, American Jim Furyk, called it "a spectacular round".
Furyk finished with a 68, level with Australian John Senden and Colombia's Camilo Villegas.
Rose came into the tournament ranked 34th in the FedEx Cup standings. His first-round effort has him poised to move into the top 30 and qualify for a spot in the finale of the playoffs, next week's Tour Championship.
Rose said he wasn't worrying about his FedEx Cup position.
"I've got nothing to lose this week," he said. "That's my strategy. That's my attitude. Right now, I'm not going to Atlanta. I've got everything to gain this week. That's really the way I'm seeing it."
While Rose has struggled of late, with 10 straight starts without a top-10 finish, Simpson has had a superb late season.
He claimed his first PGA Tour victory at Greensboro in August, then moved to the top of the FedEx Cup standings with his Deutsche Bank triumph.
"Luckily, I was able to keep the momentum in the good stretch I had in Boston going into today," said Simpson, who had six birdies with no bogeys.
"We got off to a really good start and made a few really good saves there in the middle of the round and finished with a couple birdies coming in.
"It was a good day for the tough course and tough conditions we were facing."
Wilson's 65 included an eagle at the par-five 15th, and he birdied his last hole, the par-five ninth, to share second with Simpson.
But plenty of players were finding the going more difficult.
Defending champion Dustin Johnson carded a 77 and Phil Mickelson's one-over par 72 included a double-bogey at the par-three second hole and four bogeys.
Leading first-round scores on Thursday in the $8 million USPGA Tour BMW Championship (USA unless noted, par-71)
63 - Justin Rose (GBR)
65 - Webb Simpson, Mark Wilson
67 - K.J. Choi (KOR)
68 - Jim Furyk, John Senden (AUS), Camilo Villegas (COL)
- Robert Allenby (AUS), Chad Campbell, Rickie Fowler, Sergio Garcia
(ESP), Zach Johnson, Robert Karlsson (SWE), Hunter Mahan, Geoff Ogilvy
(AUS), Chez Reavie, Jimmy Walker
70 - Jonathan Byrd, Lucas Glover, Bill Haas, Sean O'Hair, Carl Pettersson (SWE), Gary Woodland, Y.E. Yang (KOR)
71 - Aaron Baddeley (AUS), Marc Leishman (AUS)
72 - Ernie Els (RSA), Fredrik Jacobson (SWE), Martin Laird (GBR), Phil Mickelson, Rory Sabbatini (RSA)
73 - Charl Schwartzel (RSA), Jhonattan Vegas (VEN)
74 - Brian Davis (GBR), Adam Scott (AUS)
75 - Luke Donald (GBR), Brendon de Jonge (ZIM)
76 - Vijay Singh (FIJ)
77 - Jason Day (AUS), Andres Romero (ARG)