Tony Finau fired a wild and wonderful 67 to set the clubhouse target and open up a three-shot lead as the second round of the WGC-HSBC Champions moved towards its conclusion at Sheshan International Golf Club.
The American entered the day two shots behind overnight leader Patrick Reed but soon overhauled him and at one point led by three shots before an unfortunate double-bogey on the 11th.
Three birdies in his last five holes then moved the 29 year old back to 11 under, three shots ahead of Reed who had five holes left to play.
Another American in Xander Schauffele was then in the clubhouse at seven under alongside defending champion Justin Rose who had completed 13 holes.
Finau got within one of the lead as he took advantage of the par five second and a 15-footer on the fourth gave him a share.
The man from Utah then got up and down from the sand on the driveable par four seventh, holing a ten-footer to hit the front on his own.
Reed was among the late starters but it did not take him long to reclaim a share of the lead, playing a wonderful short pitch to set up a birdie on the second.
Finau birdied the par five eighth to get to double-figures but Reed's approach to the third was to eight feet and the duo were tied once more and four ahead of the chasing pack.
Reed recovered well from a poor tee-shot on the fifth but missed a short one and when Finau holed a ten-footer on the tenth, he led by two.
The Masters Tournament champion found water on the sixth to hand Finau a three-shot advantage but the leader got a nasty bounce off a sprinkler-head on the 11th to go over the back of the green and failed to find the putting surface with his third, eventually surrendering a double-bogey.
Another bogey came on the 13th after Finau found a bunker with his second meaning the lead was back at eight under where it had started the day.
A birdie after getting on the par five 14th in two then handed Finau a narrow lead and better was to come over the closing stages. He hit a brilliant approach into the 16th and got on the green at the par five last in two for a pair of birdies and a three-shot advantage.
Affiliate European Tour Member Schauffele started with seven pars but birdied the eighth before giving the shot straight back after finding sand.
He got back to seven under with a gain on the 11th but once again dropped a shot on the 16th before picking it back up on the last.
Rose birdied the second and holed an eight-footer at the third before making another birdie on the eighth to turn in 33. A stunning approach to six feet on the 11th then handed the Englishman a share of third.
American Patrick Cantlay recovered from a bogey on the first with birdies on the third, fifth, sixth, eighth and ninth to turn in 32. He then bogeyed the 14th but picked the shot back up on the 16th to sit at six under after a 68.
Reigning Race to Dubai champion Tommy Fleetwood was also at that mark with five holes to play.
Kiradech Aphibarnrat, Keegan Bradley, Emiliano Grillo and Kyle Stanley were in the clubhouse at five under.
