PEBBLE BEACH, Calif. — Phil Mickelson is closing in on three decades on the PGA Tour and a half-century on Earth, and he still feels his best golf is good enough.

He was at his best at Pebble Beach, and no one had a chance.

A Monday finish brought on by rain and a freak hail storm was only a minor inconvenience for the 48-year-old Mickelson. He played two holes just as well as the previous 16 and polished off his bogey-free final round with one last birdie for a 7-under 65 and a three-shot victory over Paul Casey in the AT&T Pebble Beach Pro-Am.

Mickelson won at Pebble Beach for the fifth time, matching the record set by Mark O’Meara. He has gone 28 years since his first PGA Tour victory and his 44th, and he joined Tiger Woods as the only players to surpass $90 million in career earnings.

“It’s a lot more work and effort to play at this level,” Mickelson said. “And I have believed for some time that if I play at my best, it will be good enough to win tournaments. The challenge is getting myself to play my best. It’s a lot more work off the course, it’s more time in the gym, it’s more time eating, it’s more time focusing, it’s all these things that go into it.

“And so it’s gratifying to see the results and to finish it off the way I did.”

Mickelson finished at 19-under 268. Casey needed Mickelson to make a big blunder on the two closing holes, and there was little chance of that. Casey at least birdied the 18th for a 71 to finish alone in second, the difference of $152,000.

He also won the Pro-Am with Don Colleran, the chief sales officer for FedEx.

This was the fourth time that Casey had a 54-hole lead of at least two shots on the PGA Tour and failed to win. The other three times he was 2-over par or worse in the final round. This time, he closed with a 71 and lost to Mickelson’s 65, which matched the low score of the final round.