Tiger Woods hit his stride today 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 tomorrow is for heavy rain that could wash out the round. Players would have to return on Monday if the course conditions and forecast allow.

The last 54-hole event on the PGA Tour was the BellSouth Classic in 2005 the week before the Masters.

Justin Leonard, who made the playing cut on the number, turned in the best score today 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. "Tomorrow, conditions are going to be tough. You just plod along and be steady and not make any bogeys."

Kevin Streelman, the 29-year-old rookie who was the last alternate to get into the Buick Invitational, finally had his introduction to Woods in more ways than one.

They shook hands on the first tee, and Streelman held his own. He hit past Woods on the opening tee shot, hit his approach to 4 feet, but missed the putt on the low side, and that became a common occurrence. Even so, he was 1 under through the day until sending a wedge long on the par-5 ninth and taking double bogey.

Streelman finished with a 75 and tumbled into a tie for 11th. But he was all smiles.

"It was one of the coolest experiences in my life," he said. "I learned a lot and did my best."

Even his best might not have mattered. Woods built a four-shot lead going into the weekend despite some scrappy play off the tee. He sorted that out today, and once the putts started falling, he was on his way.

Phil Mickelson made an early charge with a 30 on the back nine (he started on No. 10) to get within five shots of the lead. Woods holed a 10-foot birdie on the fourth, and his approach at No. 5 spun back and grazed the edge of the cup for a tap-in birdie.

He hit his tee shot on the 212-yard 11th hole to 3 feet, and two-putted for birdie on the 13th, his only look at eagle all week. Even though he was at 18 under, Woods has played the par 5s in just 6 under this week.

The only thing left to determine at the end was the size of his lead. Woods hit a 3-iron from the first cut of rough on the 18th that was all over the flag, came up short, and he was lucky the ball stayed on the bank of the pond. He chipped to a foot for birdie, then watched Cink roll in his eagle from across the green.

Woods and everyone else will find out tomorrow whether they play, but even if the fourth round can't finish until Monday, that might bring another omen to the world's No. 1 player.