Australian Jason Day used a red-hot run around the turn and a solid finish to seize a two-shot lead over Jordan Spieth after a pulsating third round of low scoring at the PGA Championship.
In pursuit of his first major victory after several close calls over the past five years, Day carded 66 in receptive conditions at Whistling Straits to post a 15-under total of 201.
The world number five picked up six shots in six holes from the ninth, including a 13-foot eagle putt at the 11th, and later rebounded from a double-bogey at the 15th by draining a curling 24-footer at the 17th.
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He could not break clear of Masters and U.S. Open champion Spieth, who reignited his hopes of a rare third major victory this year by firing a bogey-free 65 on a hot and steamy afternoon highlighted by birdies galore.
English world number six Justin Rose (68) was a further stroke back at 12 under with South African Branden Grace, who spectacularly holed out from a greenside bunker to birdie the last and card a best-of-the-day 64.
Germany's Martin Kaymer, winner of the 2010 PGA Championship played at Whistling Straits, drained three long birdie putts to shoot 65 and pull within four shots on a day when the scoring average was 70.6.
Standings (after 3rd round):
-15 Jason Day (Australia)
-13 Jordan Spieth (U.S.)
-12 Branden Grace (South Africa)
Justin Rose (Britain)
-11 Martin Kaymer (Germany)