Australia's Marc Leishman came from behind with a superb seven-under 65 to secure a one-stroke win at the Farmers Insurance Open at Torrey Pines in San Diego on Sunday, while Northern Ireland's Rory McIlroy finished joint third. 

Leishman fired five birdies on the front nine to emerge from the pack as overnight leader Jon Rahm of Spain and McIlroy faltered.

Thee Aussie had to keep his nerve on the home stretch, making three big par saves to hold the lead as Rahm - four over through a poor first four holes - flew home with four birdies and an eagle in his last six to make a two-under 70.

Ultimately the 36-year-old held on at 15-under 273 ahead of Rahm to become the second Australian tournament winner on his country's national day, Australia Day, following Lucas Herbert's playoff victory in Dubai on the European tour.

McIlroy, needing a victory to reclaim the world's number one ranking, started three shots off the pace but made three bogeys in his first four holes.

He recovered to play his last five holes of the front nine in five under par but could not make up enough ground in a one-under back nine. His three-under 69 left him tied for third with American Brandt Snedeker, three shots behind Leishman.

Tiger Woods, hoping for a PGA Tour record 83rd career victory, never came close as a 70 left him tied for ninth, on a day tinged with sadness due to the death of former basketball star Kobe Bryant.

Woods, who started his pro career the same year as the NBA superstar known as the Black Mamba, was unaware of the news until after his round.

"I didn't understand why they were yelling, 'Do it for Mamba' on the back nine," said Woods, who called it "one of the most shocking, tragic days I've ever been part of."