LOS ANGELES (AP) — Bill Haas had another bogey-free round at Riviera while shooting a 7-under 64 — the best round of the day by three shots — on Saturday to take a three-stroke lead into the final day of the Northern Trust Open.

U.S. Open champion Webb Simpson and former Masters champion Charl Schwartzel each had a 68 to be the nearest chasers, along with John Merrick, who bogeyed the last to finish with a 70.

The key for Haas was a seven-hole span in the middle of his round that he played in 6-under par, including a chip-in for eagle on the par-4 10th. He was at 12-under 201 and will try to become the eighth back-to-back winner in the 76-year history of this tournament.

"It's very difficult in this game to just pull away from the rest of the field," Haas said. "You've only seen a few guys ever really do that, and those are guys like Jack Nicklaus, Tiger Woods, Phil Mickelson. I've just got to stay in the moment, don't let my emotions get the best of me."

A year ago, Haas was two shots behind going into the final round and wound up winning in a playoff over Mickelson and Keegan Bradley. This time, he has a comfortable margin over U.S. Open champion Webb Simpson and former Masters champion Charl Schwartzel, who each thought they did well for a 68.

Luke Donald overcame a sloppy start — three bogeys in a six-hole stretch — with four birdies on the back nine to salvage a 70 that put him four shots behind, along with second-round leader Fredrik Jacobson (72).

Mickelson was hopeful of making a move and instead went the other direction. He missed three par putts of about 6 feet on the front nine and had a 72, putting him nine shots behind. Ernie Els, playing with Mickelson, also dropped shots early and dropped out of the hunt with a 73.

The round started with 20 players separated by five shots. Thanks to Haas and his flawless play, only eight players were within five of the lead.

It might not be easy for anyone to catch up to Haas if the sunshine continues to bake Riviera. The fairways were so firm that tee shots were running some 50 yards after they landed, and the greens were firm enough that balls ran out an extra two feet around the hole.

"I had a lot of 3- and 4-footers for par," Simpson said.

Haas has gone 40 consecutive holes without a bogey. The last one he made was on Thursday when he missed a 4-foot putt. But on this day, it was his birdies and one eagle that made the difference.

"I was just kind of plugging along out there and then all of a sudden, made a nice putt at 9, chip-in at 10, good up-and-down at 11," he said.

Simpson reckons Haas would have to make a few mistakes for anyone to make a big move.

"Bill is in a position, if he keeps a three-shot lead and goes and plays well again, that it's going to be hard to catch him," Simpson said. "But with the golf course this tricky, you get a guy that has a good front nine, he could be tied or even in the lead with nine to go. So anything can happen tomorrow."

Schwartzel is the only player with all three rounds in the 60s. He made two mistakes, one of them more bad luck. His tee shot on the 10th bounded through the green with such pace that it stayed toward the back slope of the rear bunker. His shot came out too soft and rolled back off the green, leading to bogey.

He came out weakly from the sand on the 15th and had to make a 6-footer to escape with bogey.

"It's easy to make bogeys," Schwartzel said. "The course got a bit firmer and, playing in the last few groups, the greens get a bit more bumpy. So it's hard to make birdies and also to keep the bogeys off the card."

"I probably won't change anything," he said. "Just keep playing the way I am and see if I can give myself chances and see what happens. I know the game is good enough to be able to win tomorrow."