Louis Oosthuizen produced a sensational birdie blitz to overhaul Rory McIlroy at the top of the leaderboard on day three of the Deutsche Bank Championship.
One behind heading into the penultimate round, Oosthuizen picked up a shot on the second, before surging clear courtesy of seven straight birdies from the fourth.
The 2010 Open Champion did drop a shot at 17, but recovered by making a four on the closing par five to complete a sizzling 63 at TPC Boston.
At 19 under, he was three ahead of World Number One McIlroy, who opened his round of 67 with back to back birdies and also improved his score on two of the final three holes.
"Louis put on a display right there," McIlroy said. "I was delighted when I got the honour back on the 12th tee."
"I've come from farther behind before. It's going to be an interesting day tomorrow."
Dustin Johnson made gains on eight holes in a 65 that lifted him into third on 13 under, a mark duly matched by Tiger Woods, who shot 68.
