Tiger Woods reacts to a missed birdie putt on the eighth hole during the third round of the Buick Open. Woods fired a 66 on Saturday in San Diego for an eight-stroke advantage.

San Diego ? Winning the Buick Invitational is now a matter of when, not who.

Tiger Woods hit his stride Saturday at Torrey Pines, missing only one green in regulation on his way to a 6-under 66 and an eight-shot lead, the largest 54-hole margin on the PGA Tour since Phil Mickelson in 2006 at the BellSouth Classic.

Woods was at 18-under 198, tying the 54-hole record at Torrey Pines set by Woody Blackburn in 1985. Woods also shattered tournament records for 54-hole lead (five shots), and appears well on his way to capturing the Buick Invitational for the fourth straight year and sixth time in his career.

Stewart Cink holed a 35-foot eagle putt on the 18th hole to lead the B-flight. That gave him a 69. One shot behind was Joe Durant, who shot a 67 on the South Course and lost ground to Woods. Durant was at 9-under 207, and when someone asked if a mercy rule was in order, he could only laugh.

“If there was ever a week for it, this might be it,” Durant said.

Mercy might come from Mother Nature. Sunshine gave way to cloud cover late in the day, and the forecast today is for heavy rain that could wash out the round. Players would have to return Monday if the course conditions and forecast allow.

Justin Leonard, who made the playing cut on the number, turned in the best score Saturday with eight birdies in a round of 65. That moved him up 44 spots on the leaderboard into a tie for fourth and gave him incentive for the final round.

“There’s two tournaments going on,” he said. “I’m going to try to win the tournament that Tiger’s not playing.”

Woods had none of it.

It was his largest 54-hole lead since he led by 10 on his way to a 15-shot victory in the 2000 U.S. Open at Pebble Beach, an ominous sign with Torrey Pines hosting the U.S. Open this summer.

“If it was over, they’d be handing out the trophy,” Woods said.