Marc Leishman has become the second Australian golfer to win internationally within 24 hours, and the fourth before the end of January.

Leishman, the 36-year-old Victorian, secured his fifth United States PGA Tour victory at the $US7.5 million Farmers Insurance Open at Torrey Pines in San Diego with a brilliant closing round of 65 to win by a shot.

It was Australia Day for golfers, with another Victorian, Lucas Herbert, taking out his first-ever victory as a professional by winning the Dubai Desert Classic on the European Tour late Sunday night eastern time.

Wade Ormsby (in Hong Kong) and Cameron Smith (in Hawaii) have already won tournaments in 2020 -- the best start by Australian men in living memory.

Leishman’s win is no surprise; he is world ranked 28 and was a significant part of Ernie Els’ International team at the Presidents Cup.

But the manner of his win was somewhat different to what we come to expect of him. He blew the field away rather than grinding them down, and it came against a field that included the world No. 2 (Rory McIlroy), No. 3 (Jon Rahm) and No. 6 (Tiger Woods) all in contention on the final day.

Leishman was tied-seventh, four from the lead held by Rahm at the start of the day. Then the Spaniard dropped four shots first five holes to open the door. Leishman bombed a birdie putt at the first from more than 12 metres; he hit the flag with a fairway bunker shot at the fourth, and birdied five of his first eight holes to seize the lead.

By the time he got up-and-down from a greenside trap at the par-five 13th for birdie, he led by three and from there, he was allowed to cruise, losing his tee shots right but scrambling his pars. At the 14th, he had to make a par-save from four metres but calmly rolled it in. Similarly at the 15th his chip from the fringe was short but he made the par-save.

His only bogey of the day came at the par-four 17th where he failed to get up and down from the greenside bunker, but by then, he was two shots ahead. Then Rahm birdied the 17th from close range, and once again, Leishman had to step up.

He wedged it close at the 18th and rolled in the putt from just outside two metres for birdie, his eighth of the day, posted 15-under par and waited for Rahm to complete the 72nd hole, needing eagle for a playoff.

Rahm drove it long and hit the back of the green in two, but when his long eagle putt trickled left of the cup, Leishman had the prize.

Leishman had previously won the Travelers Championship in 2012, the Arnold Palmer Invitational and the BMW Championship in 2017 and the CIMB Classic in Korea in 2018. The man from Warrnambool on Victoria’s south-west coast has won 13 tournaments around the world and will end up being regarded as one of the best-ever Australian golfers, even though his quiet manner and humble way leaves him without a high profile.

His winning prize cheque is $US1.35 million. "No. 5, that sounds pretty good," he said afterward. "And on Australia Day ...."

Leishman has lost 10 kilograms in the past six months as a plan to help him deal with a back injury. He has donated tens of thousands of dollars to the Australian bushfire relief funds and is using his own foundation Begin Again, formed after the near-fatal 2016 illness of his wife Audrey, to raise money for the cause.

"It's awesome to be able to support the people who are struggling back home in Australia with the bushfires especially, and for the people in America who'e experienced what Audrey experienced," he said. "This feels pretty amazing. I wasn't expecting this at the start of the day. I'm elated."

Woods, who was told of the death of his friend Kobe Bryant as he finished his round, shot a closing 70 to finish tied-ninth

Of the other Australians, Jason Day (tied-17th), Cameron Percy and Cameron Davis (tied-36th) were the best.

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