Final flourish lifts Mickelson into PGA Riviera lead Phil Mickelson chipped in for birdie at the final hole to seize a one-shot lead in the wind-whipped first round of the US PGA Tour's $6.6 million-dollar Northern Trust Open. Mickelson, who surged to victory with a sparkling 64 last Sunday at the Pebble Beach National Pro-Am, on Thursday broke out of a tie at the top of the leaderboard, his five-under 66 on the par-71 Riviera Country Club course giving him a one-shot lead over JB Holmes and Hunter Mahan. Holmes, on the comeback trail after brain surgery brought his 2011 season to a premature halt in September, opened fast with four birdies in his first five holes despite difficult gusting winds. Mahan, who like Holmes started on the 10th tee, surged up the leaderboard with four birdies in a row from the fifth hole before he closed his four-under 67 with a par at the ninth. All three were among the players whose afternoon tee times were pushed back almost half an hour as winds gusting up to 35 miles per hour (56 kph) slowed play in the morning. Jonathan Byrd's three-under par 68 was the best round of the chilly, blustery morning and left him tied for fourth with Sweden's Carl Pettersson -- who completed his round just as darkness halted play with 30 players still to finish on Friday morning. "It was a challenging day today because Riviera doesn't give you great opportunities to run balls onto the green," said Mickelson, who opened his round with a birdie at the par-five first. His six birdies also included a 30-footer at the par-three fourth, his lone bogey of the day coming at 16. Mickelson said "somewhat receptive" greens kept the wind from making the course unfair. "You could keep the ball underneath the wind, underneath the tree line and still get it to stop somewhat on the greens," he said. After his bogey, and his inability to pick up a shot at the par-five 17th, Mickelson was especially pleased with his unlikely birdie at the last, where his speedy downhill chip from behind the green rolled right in. "It feels really good to get that one extra shot," said Mickelson, who won back-to-back titles here in 2008 and 2009. While Mickelson arrived at Riviera buoyed by his stirring victory at Pebble Beach, Holmes is slowly regaining his form after surgery to repair Chiari malformations -- a structural defect where the brain and spinal cord connect. He was diagnosed after bouts of dizziness and vertigo, and needed a second round of surgery in October. "It's improved every week," said Holmes, who is making his fourth start of a season he opened at Torrey Pines last month. I'm probably not quite 100 percent, but I definitely feel a whole lot better with my swing and my game than I did at San Diego for sure. South Korea's KJ Choi completed his two-under early and was among half a dozen players in the clubhouse on 69 that included Spain's Sergio Garcia and Stewart Cink. World number one Luke Donald, who in 2011 became the first player to win both the European and US tour money titles in one season, opened his US PGA Tour campaign with a one-under 70.