Justin Rose slipped one stroke behind the clubhouse leader during the opening round at the BMW Championship.
The Englishman was in superb form as he carded eight birdies in the first 11 holes on a warm morning at Cog Hill.
He held a four-stroke lead at eight under par but could not maintain the momentum and ran up two late bogeys for a six-under-par 65.
He was one stroke behind American Jonathan Byrd, who stormed home with three birdies in his final four holes, while Tiger Woods shot a four-under 67 which was marred only by a late double-bogey.
Despite his lofty world ranking of 15, Rose is still seeking his first American victory, and he could hardly have hoped for a better start.
He was on song with his iron play right out of the blocks, rifling his approach shot to inside eight feet at the par-four first, before holing the putt for a confidence-boosting start.
Two holes later he hit another precise iron to just three feet for his second birdie of the day, and it was the same story at the par-four fourth as he almost knocked the pin out again.
Rose picked up another stroke at the par-three sixth, this time hitting his tee shot to five feet, and he finally made a decent length putt of 15 feet for yet another birdie at the par-four seventh.
He missed his first green of the day at the next, but got up-and-down to save par, before picking up yet another birdie at the par-five ninth, sinking a 45-foot putt.
Making the turn at six-under, he continued to attack starting the back nine, adding birdies at the next two holes, sinking a 20-foot effort at the par-four 10th, before two-putting at the par-five 11th.
But the birdies dried up after that, with bogeys at the par-five 15th and par-four 18th not exactly what he had in mind.
Compatriot Ian Poulter was going along quite nicely at two under after 13 holes, while Luke Donald was struggling at one over after 14 holes.
This event is the third in the new four-tournament FedEx Cup play-off series. Only 30 players will advance to next week's Tour Championship.
