Los Angeles ? Phil Mickelson showed up early Saturday to work with swing coach Butch Harmon, then ran off four straight birdies late in his round for a 9-under 62 to build a four-shot lead going into the final round of the Northern Trust Open.

Five players had at least a share of the lead at one point in the third round, but what had been shaping up as a shootout at Riviera soon turned into a showcase for Mickelson.

It began with a tee shot into 4 feet on the par-3 14th for the outright lead. Mickelson followed that with an 8-foot birdie on the 15th, a 35-foot birdie on the 16th, and an up-and-down from the bunker on the par-5 17th for his fourth straight birdie. He had a 10-foot birdie putt on the 18th to tie the course record, but hit the putt too hard.

Mickelson was at 16-under 197.

Andres Romero of Argentina birdied his last three holes for a 65 and could remain the last obstacle for Mickelson. It was Romero who made 10 birdies in 16 holes during the final round at Carnoustie two years ago when he nearly won the British Open.

They will be joined in the last group by Fred Couples, who was poised to give himself a good chance to win only to have a familiar figure spoil the occasion. Mickelson and Couples were in the last group at the 2006 Masters when Lefty outlasted him over the final five holes.