Louis Oosthuizen birdied four of five holes on the back nine Saturday to move two clear of the field after three rounds of the Houston Open.
The 2010 British Open champion fired his second straight six-under 66 to finish 54 holes at 17-under-par 199. He missed the tournament's 54-hole scoring record by one stroke.
Oosthuizen's lone PGA Tour win was at the British Open. He has won four times over the last three years on the European Tour.
Hunter Mahan fired a seven-under 65 to jump into second place at minus-15. He claimed his second WGC earlier this year when he won the WGC - Accenture Match Play. That was this fourth PGA Tour title and first since winning the 2010 WGC - Bridgestone Invitational.
Brian Davis, who shared the second-round lead with Oosthuizen, carded a three- under 69 to join Carl Pettersson (67) in third place at 14-under-par 202. James Driscoll (71) is two strokes back at minus-12 on the Tournament Course at Redstone Golf Club.
Defending champion Phil Mickelson managed his second straight two-under 70 in round three. He stands alongside Ryan Palmer (66) and PGA Champion Keegan Bradley (69) in sixth place at 11-under-par 205.
The second round was completed earlier Saturday after a weather delay on Thursday pushed the tournament back. The event is back on schedule despite the fact that 90 players made the cut after two rounds.
Outside of the majors, the 1981 Travelers Championship was the only other time more than 90 players made the 36-hole cut.
MORE TO FOLLOW.