Humble - Former British Open champion Louis Oosthuizen birdied five of the last seven holes to charge two shots clear in the third round of the weather-delayed Houston Open here in Texas on Saturday.
The smooth-swinging South African recovered from bogeys on the first two holes to card a six-under-par 66 at the rain-softened Redstone Golf Club in the final PGA Tour event before next week's Masters.
Oosthuizen, who romped to a seven-stroke victory at the 2010 British Open, launched his late surge with four consecutive birdies from the 12th to post a 17-under total of 199.
American Hunter Mahan was alone in second place after carding a 65, with Swede Carl Pettersson (67) and Britain's Brian Davis (69) a further stroke back at 14 under.
For the second round in a row at Redstone, players were permitted to lift, clean and replace their balls on a course that had been saturated by more than an inch of rain on Thursday.
"I had to compose myself," Oosthuizen told reporters, referring to his bogey-bogey start. "Other than that, I hit it well and started making a few putts on the back nine.
"I was driving it well, my iron play the whole week has been really good and I just made some good putts today.
"The greens here are really fast, which I enjoy. If it's not windy here, you feel like there are a lot of birdies out there."
Asked how he would approach Sunday's final round, Oostuizen replied with a smile: "Pretty much the same as today, try and not start bogey-bogey.
"It's always a good opportunity going in with a lead. I think it's going to be good fun tomorrow."
Defending champion Phil Mickelson was among a group of three players tied for sixth at 11 under after shooting a three-birdie 70.
Three-times major winner Ernie Els, who needs to win the Houston Open to qualify for next week's Masters, was at eight-under 209 after shooting a second successive 69.
"I've just got to stick to what I'm doing," said the South African former world number one. "I'm playing really well.
"Obviously, I would love to get a win. I'd like to play a solid round of golf tomorrow. If it really gets going, that will be really a plus."
Earlier in the day, American Jeff Maggert birdied three of his last eight holes to grab a one-shot lead when the weather-delayed second round was finally completed at Redstone to get the tournament back on track.
The 48-year-old went on to shoot 76 in the third round to finish a long day tied for 14th at eight under par.
Maggert, a three-times winner on the PGA Tour, is playing his ninth and final event this year on a major medical exemption following shoulder surgery and needs $202,609 to retain his status for next season.
Scores from the Houston Open in Humble, Texas on Saturday (par-72):
199 Louis Oosthuizen (South Africa) 67 66 66 201 Hunter Mahan (U.S.) 69 67 65 202 Carl Pettersson (Sweden) 65 70 67
Brian Davis (Britain) 68 65 69 204 James Driscoll (U.S.) 67 66 71 205 Ryan Palmer (U.S.) 71 68 66
Keegan Bradley (U.S.) 67 69 69
Phil Mickelson (U.S.) 65 70 70 206 John Senden (Australia) 72 65 69
Boo Weekley (U.S.) 69 67 70
John Huh (U.S.) 66 70 70
J.B. Holmes (U.S.) 68 67 71
Tommy Gainey (U.S.) 68 67 71 208 Jeff Overton (U.S.) 69 70 69
Ernie Els (South Africa) 70 69 69
Lee Westwood (Britain) 68 70 70
Thomas Bjorn (Denmark) 69 69 70
Pat Perez (U.S.) 68 69 71
Brandt Jobe (U.S.) 68 69 71
Vaughn Taylor (U.S.) 69 67 72
Jeff Maggert (U.S.) 66 66 76 209 Bryce Molder (U.S.) 70 70 69
Johnson Wagner (U.S.) 68 71 70
Yang Yong-Eun (South Korea) 69 71 69
Cameron Tringale (U.S.) 69 70 70
Marc Leishman (Australia) 70 70 69
Danny Lee (New Zealand) 69 68 72
Henrik Stenson (Sweden) 69 68 72
Bud Cauley (U.S.) 67 69 73 210 John Mallinger (U.S.) 70 70 70
Scott Piercy (U.S.) 70 70 70
Nathan Green (Australia) 70 70 70
Sean O'Hair (U.S.) 70 71 69
Harris English (U.S.) 69 68 73
Tim Herron (U.S.) 74 68 68
Jonas Blixt (Sweden) 70 66 74 211 Fred Couples (U.S.) 67 73 71
Tommy Biershenk (U.S.) 72 67 72
Jim Herman (U.S.) 68 70 73
Erik Compton (U.S.) 71 67 73
Mark Anderson (U.S.) 71 70 70
Blake Adams (U.S.) 67 71 73
Kyle Reifers (U.S.) 68 69 74
Chad Campbell (U.S.) 69 67 75
Angel Cabrera (Argentina) 65 70 76
Greg Owen (Britain) 66 69 76 212 Brendon De Jonge (Zimbabwe) 70 70 72
Graeme McDowell (Britain) 70 69 73
Ben Crane (U.S.) 69 70 73
Rickie Fowler (U.S.) 68 70 74
Billy Mayfair (U.S.) 70 71 71
Mathew Goggin (Australia) 70 72 70
Rod Pampling (Australia) 73 69 70
Will Claxton (U.S.) 70 72 70 213 Roberto Castro (U.S.) 71 69 73
Steve Stricker (U.S.) 68 70 75
Steve Wheatcroft (U.S.) 68 72 73
Shawn Stefani (U.S.) 71 71 71
Shaun Micheel (U.S.) 70 72 71 214 Joe Ogilvie (U.S.) 71 69 74
Ricky Barnes (U.S.) 66 74 74
Jamie Lovemark (U.S.) 70 70 74
Jason Bohn (U.S.) 69 72 73
Cameron Beckman (U.S.) 74 67 73
Troy Matteson (U.S.) 73 69 72
Ted Potter Jr. (U.S.) 74 68 72
John Merrick (U.S.) 70 72 72
Jhonattan Vegas (Venezuela) 72 70 72
Troy Kelly (U.S.) 71 71 72 215 Miguel Carballo (Argentina) 74 68 73