Day one leader Rory McIlroy went from two in front to five behind after a disappointing finish to his second round in the WGC-HSBC Champions in China.
A last-hole gamble backfired on McIlroy as Dustin Johnson stormed into a commanding lead in the second round at Sheshan International Golf Club on Friday.
McIlroy held a two-shot lead after a sparkling opening 65 and was three clear when he followed five straight pars with birdies at the sixth, seventh and eighth.
However, the back nine was an entirely different story as McIlroy bogeyed the 11th and 15th after finding sand and then finished with a six at the par-five last after going for the green in two but coming up short and finding water .
That left the two-time major winner on seven under and five shots behind Johnson, who had charged through the field with a course record-equalling 63.
"Disappointing, frustrating," was how McIlroy summed up his round to reporters.
"I obviously played nicely on the front nine and then started to hit a lot of sloppy shots on the back. I missed the last six greens in a row, seven on the back nine, so a bit of work is needed on the range this afternoon.
"I hit a couple of bad shots and then I guess I let it affect me a little bit and then I started to doubt myself sometimes. I didn't hit a lot of quality shots on the back nine.
"It would have been nice to play a bit better and start tomorrow with a few more shots in hand but I guess I'm in a decent position going into the weekend, and still have a great chance at winning this tournament."