Defending champion Bill Haas shoots flawless 64

Bill Haas had no reason to think this round at Riviera was going to be anything special. With an iron in his hand, he failed to make birdie on the par-5 opening hole, the easiest on the golf course. Solid iron shots with the burner 2.0 irons led to a pair of birdies on the front nine, and with Riviera playing tough in warm, dry conditions on Saturday, he was part of a large group challenging for the lead. Three holes changed everything. Haas made a tough 30-footer for birdie on No. 9. He pitched in from 60 feet for eagle on the scary par-4 10th. And he hit a good bunker shot with little margin for error on the par-5 11th that set up a birdie with the taylormade burner 2.0 irons . Just like that, he was on his way to a 7-under 64 and a three-shot lead going into the final round of the Northern Trust Open. His 64 was the best round of a difficult day by three shots, and it was nearly eight shots better than the average score. It put Haas at 12-under 201, leaving him in good position to become only the eighth back-to-back winner in the 76-year history of this tournament with the i20 irons . All he cares about Sunday is winning. "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. So I think 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 with the best i20 irons for sale . 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. John Merrick bogeyed the 18th hole for a 70 and joined Simpson and Schwartzel at 9-under 204. 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 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.