Golf-Day on verge of BMW victory and world number one ranking

LAKE FOREST, Illinois, Sept 19 (Reuters) - Jason Day stayed on track for his fourth victory in six starts when he birdied the final hole to earn a six-stroke lead after the third round at the BMW Championship on Saturday. The Australian was not at his very best, but a two-under-par 69 at Conway Farms was enough to increase his lead after he started the day five shots clear. He posted a 20-under 193 total with one round left in the third of the PGA Tour's four FedExCup playoff events. Americans Scott Piercy (67) and Daniel Berger (70) shared second place at 14-under. World number three Day, in posting the largest 54-hole lead on the PGA Tour this year, set himself up to claim the world number one ranking. If he wins on Sunday, Day will overtake current top dog Rory McIlroy, who shot 67 to be fourth at 13-under. (Editing by Andrew Both)