Mickelson Outlasts Couples in a Playoff : Golf: Left-hander, 23, becomes youngest to win four PGA events, breaking Nicklaus’ record.

In the battle between Phil Mickelson and Fred Couples for first prize in the regular PGA Tour portion of the $1.5-million Mercedes Championship, it became a case of who bogeyed last.

Couples, the veteran, was the loser Sunday on the second extra hole at La Costa, failing to sink a 12-foot par putt.

For Mickelson, 23, it was indeed an exciting day. Not only did his family see the feat, but he became the youngest to win four PGA events, breaking Jack Nicklaus’ record by three months.

The left-hander also beat Nicklaus by three shots as the regular Tour players put an end to the seniors’ dreams of an overall victory in the simultaneous tournaments played from the same tees by both age groups.

Mickelson and Couples were 12 under par at 276. Tom Kite, second last year, also beat the old-timers, finishing third at 278. Defending champion Davis Love III made a late run, but fell four shots short at 280.

Mickelson, after being six under for 15 holes on the final round, started hooking his drives. He bogeyed the 16th to allow Couples to pull even.

On the 569-yard par-five 17th, Couples, trying to lay up from the rough in the right, hit a two-iron. His body was well in front of his club head and the ball sliced into the water on the right.

Mickelson, with a chance to go two shots ahead, pulled a 12-foot birdie putt and Couples bogeyed. Mickelson needed only to par 18 to win. His second shot was slightly below the green, 30 feet from the pin. He took a putter and blasted the ball 15 feet past the cup. Couples made a routine par and it was back to the 18th tee for the playoff.

Couples missed a chance to win when his 22-foot downhill putt barely curved around the cup. Couples, who had hit his driver far to the right into the trees on No. 10 during most of the tournament, went to his three-wood for the playoff. He hit a very slight hook, but it rolled down the hill and into the sand.

“I just didn’t have enough room to go for the green,” Couples said. “I had to get it over the water and then pitch up. I left it 12 feet short.

“It would really have been nice to win the first tournament of the year, but it was a fun match. It was just hard to lose. I’ll get over it in about an hour. Phil is a fine young golfer, and he’ll win many more times.”

Mickelson has become tough to beat in his home San Diego area. Last spring, he won the San Diego Open at Torrey Pines, his favorite course.

“This was really a thrill,” he said. “It qualifies me for the World Series and makes certain I’ll get to come back here. . . . What could be better than winning with my family and friends watching?

“I really didn’t expect to do that well. I had hardly touched a club in the last month. But I owe much to Dean Reinmuth, my coach. He has been helping me with my swing.”

The sky was cloudy when the seniors teed up in the morning, but it turned out to be the fourth consecutive perfect day, with little wind.

Couples birdied the first two holes and the fourth. Meanwhile, Mickelson barely missed an eagle on two and also birdied three and six. Despite bogeying No. 5, the leaders were pulling away.