Branden Grace made a surge through the field as the final round of the US PGA Championship was set up for a dramatic conclusion at Baltusrol Golf Club.
Jimmy Walker came into round four with a one-shot lead after playing his third round on Sunday morning in 68 to get to 11 under, and he remained at that mark with four opening pars.
Storms on Saturday had meant the final five groups faced 36 holes on the final day but Grace was moving through the pack and, after completing a 66 in the morning, the South African continued that form into his last 18 holes.
The seven-time European Tour winner picked up four shots in 15 holes to get within a shot of Walker as both men went in search of a maiden Major Championship.
Open champion Henrik Stenson was also at ten under with a birdie on the sixth, a shot clear of defending champion Jason Day and Brooks Koepka, and two ahead of clubhouse leader Tyrrell Hatton.
Grace made an early move with birdies at the second, fourth and seventh to turn in 33 and join the group at nine under.
Stenson required a nervy eight-footer on the first but managed to save par, a feat that was not matched by Day who dropped his first shot in 21 holes after going a long way right off the tee to hand Walker a two-shot lead.
Grace then maintained his charge with an approach to six feet on the 13th and he moved into double figures.
Day was ragged off the tee again on the third and dropped another shot and, while Walker also went wide with his first shot on the same hole, the 37 year old recovered well to save par.
Stenson then played a brilliant shot out of the rough to set up a birdie on the sixth as he hunted a second Major Championship in 14 days while Day made his first birdie of the round on the fifth.
Koepka began his round with six straight pars.
Hatton's 68 was his third round of the week in the 60s and the Englishman was on course for an impressive finish after his tie for fifth at The Open Championship.
Padraig Harrington - the 2008 champion - was then at six under after following up his brilliant 65 with a 68.
