He just couldn't beat the darkness.

On a wild day of weather even by Pebble Beach standards, rain gave way to sunshine that gave way to a hail storm, causing two delays. The delays kept Mickelson from finishing off a remarkable rally in which he turned a three-shot deficit against Paul Casey into a three-shot lead until it was too dark to finish the last two holes.

Mickelson at least wanted to try.

"I can see fine," he said to a PGA Tour rules official as they walked up the 16th fairway.

"We can't finish two holes in six minutes," Casey said to the official — he opted to mark his ball on the 16th green.

Mickelson had already made his par on the 16th and was 6 under for the day, with no bogeys on his card, and 18 under for the tournament. Casey has a 3-foot par putt to stay three shots behind when they return Monday morning to play the par-3 17th and the par-5 18th.

Mickelson made his big run starting with a 9-iron to a foot behind the cup on the par-4 ninth. That was the start of a five-hole stretch in which Mickelson made three birdies and Casey had two bogeys, taking Lefty from two behind to three ahead.

"I didn't make anything. I hit some good golf shots and didn't get anything out of it today," Casey said. "Phil has put together a spectacular round of golf so far — 6 under, no dropped shots. Remarkable stuff."

Even as Mickelson strongly hinted at wanting to finish, Casey stood his ground.

Casey was at 15 under, tied with Scott Stallings, who closed with a 66. Along with an outside chance at forcing a playoff, finishing alone in second instead of a tie is a difference of $152,000, along with world ranking points and FedEx Cup points.

Mickelson was standing on the 17th tee when he heard the horn sound to stop play, and he shook his head.

The rest of his day was far better than the weather.

Mickelson is on the verge of winning for the 44th time in his career, and matching Mark O'Meara with five victories at a tournament he first played in 1995.

It also would be his first victory on American soil since the Phoenix Open six years ago.