The WGC-HSBC Champions looks to be going down to the wire with a four-way tie at the top of the leaderboard at the midway point in Shanghai.
Russell Knox, Danny Willett, Ross Fisher and Kevin Kisner were locked together on 17 under at Sheshan International.
Scotland's Knox was the first man out on the course as he returned to complete his third round on the 18th and he made a birdie to join Kisner at 16 under.
When the fourth round began, it was soon clear that low scores would be possible as Willett flew out of the blocks with four birdies in a row to get to 11 under.
Jordan Spieth's 63 had lit up the course on Saturday but he began with a bogey before bouncing back with a birdie on the second.
Fisher made birdies at the second and third to get to 15 under but Knox and Dustin Johnson repeated the trick in the final group to stay ahead.
Daniel Berger and Willett continued their fine rounds to both turn in 30 and when Willett made a seventh birdie of the day on the 10th, both those men were at 14 under and right in it.
Branden Grace was also on the charge and a fifth birdie in seven holes on the eighth got him to 16 under alongside Kisner who made a gain on the sixth.
But Knox holed a great 12 footer to open up a two-shot lead before a great approach on the seventh gave Johnson a tap in and the gap was back to a single stroke.
Patrick Reed moved to 15 under with a birdie on the eighth and Willett soon joined him as his second shot got to within three feet on the 13th for an eighth birdie of the day.
Another birdie from Willett on the 14th made it nine for the day and he was within two of the lead with Fisher who picked up a shot on the eighth.
Kisner also birdied the eighth to get to within one but Johnson made a double bogey after seeing his ball roll into the water.
Knox then bogeyed the ninth to drop to 17 under and birdies for Fisher on the 10th and Grace on the 11th meant there was a four-way tie at the top.