LAS VEGAS -- Webb Simpson was far from comfortable with a four-stroke lead at TPC Summerlin.
"This is a golf course where guys can shoot, as we've seen this week, 8, 9, 10, 11 under," Simpson said. "So, I have to go out with a mindset of attacking and trying to make birdies."
Simpson maintained his four-shot advantage Saturday in the Shriners Hospitals for Children Open, birdieing four of the last seven holes for a 4-under 67.
"I think the key tomorrow is to, No. 1, stay patient again in case I do get off to another slow start," said Simpson, who missed a playoff -- that Jonathan Byrd won with a hole-in-one on the fourth extra hole -- by a stroke in 2010 after making a double bogey on the par-3 17th.
Making his first start since helping the U.S. win the Presidents Cup, the 2012 U.S. Open champion was 19 under overall. He opened with rounds of 64 and 63.
"The conditions were perfect," Simpson said. "I knew guys were shooting low numbers. I felt like I was playing good enough. I just was shooting pretty bad -- parred 9, dropped the shot at 11. So, it was frustrating. But my caddie just told me to stay patient and let the birdies come. And that's what happened. I made some putts coming in."
Chesson Hadley was second after a 67, birdieing the short par-4 15th and following with a hole-out for an eagle on the par-5 16th.
"They waved us up on 15 and I just roasted a driver up there," Hadley said. "I think it hit perfectly into the hill and dribbled up there to about 10 feet. I hit a good putt. It was just a little to the left, so it was a nice tap-in birdie. So that was good.
"Then I drove it right on 16, and I laid up to the perfect number. And my first thought when I hit it was, `Please go a little.' Then I saw it take the first bounce and it looked like it just one hopped right in the bottom of the stick. That was huge."
The Web.com Tour Championship winner last month, Hadley is making his fourth career PGA Tour start. He and Simpson are both from Raleigh, N.C.
"Webb and I grew up playing together," Hadley said. "He's always been more successful earlier than I have been. And you know, he's been such a good role model and just influence for the game as far as his faith is concerned. I'm just looking forward to playing with him tomorrow."
Jeff Overton was third at 14 under after a 68.
O'Hair eagled the 15th.
"I've been playing some nice golf, and it was nice to come out today and get started off quick," O'Hair said. "I was 3 under pretty quickly and turned at 4, and kind of started off slow on the back nine, but that eagle helped on 15. So, it was just all in all a great day."
O'Hair had to play the four-event Web.com Tour Finals to regain his PGA Tour card.
"I think it was a tough time this year for me, especially late because I was realizing I was going to lose my card," O'Hair said. "I just had to get my mind right going into those Web.com events. I knew I had an opportunity to get my card back, but I had to be in a right spot mentality. It was a disappointing time for me.
"I was able to get my mind right, and I played fairly well. ... I really feel good about my game right now, everything about it, from putting, ball-striking. I really feel like I can play some great golf right now. I think it helped me to kind of go back to basics and simplify my game."
Henry has shot 71-70 after opening with a course-record 60. McGirt shot 64, Ishikawa had a 68, and Moore and Knox shot 69.
Daniel Summerhays had a 68 to reach 11 under. He eagled the par-5 13th and 16th holes.
Jimmy Walker, the winner of the season-opening Frys.com Open last week in California, was 10 under after a 64.