Dustin Johnson fired a stunning 63 on day two at Sheshan International Golf Club to take a one-shot lead into the weekend at the WGC-HSBC Champions.
The World Number One is looking to become the first player in history to win three of the four World Golf Championships in a single season after claiming the WGC-Mexico Championship and WGC-Dell Technologies Match Play.
Johnson began the day four shots off the lead of Brooks Koepka but he finished his day with four birdies in a back nine of 29 to surge clear of the field at 13 under.
Koepka fought back with two birdies in his last three holes in a 68 to sit at 12 under, three shots clear of Kiradech Aphibarnrat and Justin Rose who led the European Tour charge.
Both Aphibarnrat and Rose shared the lead at times on Friday but Johnson's back-nine surge put him a commanding position - an achievement all the more remarkable considering he only used his putter for the first time shortly before teeing off.
"Obviously I played very well today but I actually got a putter like about 20 minutes before I teed off, it's a Spider, so it's one that I've used before," he said.
"I wasn't really pleased with the one I played with yesterday so the guys here in China made me one. I got it right before I walked to the tee. I hit a few putts on the practice green with it and I was like, 'oh, this will work pretty well'. Went out and holed a lot of putts today, so I kind of like it.
"It's a golf course that I enjoy playing. It suits my eye very well.
"You've got to drive it well. For me, if I drive it good out here, I feel like I can make a lot of birdies. The par fives, I can reach all the par fives if I drive it in the fairway.
"The rest of the holes, I feel like if I'm in the fairway I can attack the golf course."


Koepka made a flying start, holing from 18 feet on the opener and then capitalising on the second after finding the green in two to establish a two-shot lead.
He would then make 13 pars in a row as Johnson surged through the field.
The 2013 champion had birdied the two par fives on the front nine and the tenth and when he put his tee-shot to five feet on the 12th, he was two back.
Another gain was to follow from ten feet on the next and while Johnson failed to take advantage of the par five 14th, he would finish with four more birdies.
He moved himself into double figures with a 12-footer on the 15th and put his approach to five feet on the next to hit the front on his own. An excellent tee-shot on the 17th made it three birdies in a row and a gain on the par five last gave him a three-shot lead in the clubhouse.
Koepka then came close to driving the par four 16th and got up and down for a birdie before rolling an excellent putt over the ridge on the 17th.
Thai Aphibarnrat birdied the second to share the lead in the early stages and a fine tee-shot on the sixth kept him well in the hunt at the turn.
A double-bogey after a poor tee-shot on the 12th dropped him back but he took advantage of the 14th, hit an approach to tap-in range on the 16th and a brilliant tee-shot on the next before bogeying the last.
Rose had taken advantage of the par fives on the front side with birdies on the second and eighth and when he rolled a putt over the ridge and into the cup from a long way out on the ninth, he turned in 33.
The 2013 US Open champion then put his approach to the 11th to tap-in range but a poor tee-shot saw him a drop a shot on the next.
A beautiful chip at the 14th and an excellent approach into the 16th helped him share the lead before he too dropped a shot on the last.
Patrick Reed came home in 32 in his 70 to sit at eight under, a shot clear of fellow European Tour Members Matthew Fitzpatrick and Henrik Stenson, and Americans Brian Harman and Matt Kuchar.
Rafa Cabrera Bello and Tyrrell Hatton were then seven shots off the lead.