* American Simpson fires a 67 to retain control
* Birdies four of last seven holes
* Rookie Hadley alone in second place
Former U.S. Open champion Webb Simpson moved closer to a fourth victory on the PGA Tour as he maintained a commanding four-shot lead after Saturday's third round of the Shriners Hospitals for Children Open in Las Vegas.
Though not quite matching the high standard of play he produced over the first two days at the TPC Summerlin, the American finished strongly with four birdies in the last seven holes to card a four-under-par 67.
That left Simpson at 19-under 194 in the second event of the PGA Tour's 2013-14 season, with 26-year-old rookie Chesson Hadley alone in second place after eagling the par-five 16th on the way to a 67.
Former U.S. Ryder Cup player Jeff Overton (68) was a further stroke back at 14 under, one ahead of fellow American Jason Bohn (69).
Simpson, however, commanded the spotlight as he recovered from an early bogey to stay atop the leaderboard on another ideal day for low scoring in the high Nevada desert where there was barely a breath of wind.
"The greens were a little more firm, a little burned out and a little faster, and I think I was a little too tentative," Simpson told Golf Channel when asked to explain his slow start to the third round.
"The speed of my long putts kind of hurt us on the front (nine). I would run them four or five feet by, or leave them short. I couldn't really get a feel for it but finally on the back nine I got some birdies going."
Four ahead overnight, the 2012 U.S. Open champion briefly dropped back into a tie for the lead with Bohn at 14 under after running up a three-putt bogey at the par-four third.
However, he immediately recovered with birdies at the fourth and fifth to move two strokes clear, then parred the next four holes to reach the turn with a three-shot advantage at 16 under.
Simpson made another misstep at the par-four 11th, finding the left rough off the tee and failing to reach the green in two on the way to a bogey for his lead to be cut to two.
Once again, though, he quickly rebounded with consecutive birdies, sinking a 12-footer at the par-four 12th and a 25-footer at the par-five 13th to regain a four-stroke cushion.
Simpson said that a chat with his experienced caddie Paul Tesori helped him regain consistency after his wayward swing on the 11th tee.
"He just gave me a pointer for my pre-shot routine," explained Simpson, who has not missed a cut since early June and is coming off a fourth-place finish at the 2013 season-ending Tour Championship.
"I started swinging good down the stretch so, thanks to him, I made a few birdies coming in."
Simpson picked up further shots at the driveable par-four 15th, where he two-putted from the fringe, and at the par-five 16th, where he narrowly missed an eagle putt from 32 feet before tapping in for birdie.
He then safely parred the last two holes to remain four strokes clear in pursuit of his first PGA Tour win since the 2012 U.S. Open at Olympic Club outside San Francisco.
Asked what mind-set he would take into Sunday's final round, Simpson replied: "I think we are going to have good weather again so we're going to stick with our game plan.
"We're going to try and go out, hopefully get off to a better start tomorrow, and make some birdies. The better I play, the harder it is for them to catch me so that's kind of my mind-set."
Sean O'Hair fired a best-of-the-day 63 to finish at 12-under 201, level with five others including fellow American William McGirt (64), Scotland's Russell Knox (69) and Japan's Ryo Ishikawa (68).