Louis Oosthuizen fired a superb second-round 63 to take control of the WGC-HSBC Champions event in Shenzhen, China.
The South African, joint leader after round one, holds a five-stroke advantage at the halfway stage after his nine-under-par effort at Mission Hills.
The 30-year-old quickly put a bogey at the second behind him to reach the turn in 31 before more birdies at 10, 11, 15 and 16 saw him surge clear of the chasing pack.
Countryman and fellow Open champion Ernie Els moved into contention by matching Oosthuizen's 63 and is now level at -11 with the other overnight leader Adam Scott, who carded a 68.
Portugal Masters winner Shane Lowry continues in fine form and a 68 leaves him a shot further back alongside American Jason Dufner (66), with fellow Ryder Cuppers Phil Mickelson and Dustin Johnson next.
Mickelson had put down an early marker for Oosthuizen by reaching the turn in 31 courtesy of two eagles and then rolled in an 18-footer for birdie at the 12th.
But the veteran gave one back and then double-bogeyed the 18th to finish the day seven off the lead.
Luke Donald was solid, if nothing else, as he recorded back-to-back 68s, while Ian Poulter is in a group alongside Lee Westwood a further shot behind after going out in 30, only to be birdie-less coming home and settling for a 68.
Defending champion Martin Kaymer is in the same group after a 69 that included a triple-bogey seven at the 15th, while another shot went two holes later.
But the biggest disappointment of the day was Bubba Watson, who was one off the lead overnight and going along steadily until making eight at the long 15th, eventually recording a sub-standard 72.