Day captured his first-ever professional event on home soil, shooting a final-round 70 to defeat Denmark’s Thomas Bjorn (71) by two strokes for a 10-under par 274.
Adam Scott stormed home with the best round of the day, a 66, to finish third and ensure Australia beat the United States to win the team title for the first time in 24 years.
Day came into the event with the tragic news of the death in the Philippines of his grandmother, six young cousins and an uncle at the hands of Typhoon Haiyan.
His Filipino-born mother, Dening, was in Melbourne to watch her son outlast Bjorn, who bogeyed the last as Day sunk a par to earn the US$1.2 million winners’ cheque.
American Matt Kuchar (278) finished fourth in the individual event with Japan’s Ryo Ishikawa (281) coming fifth.
With Scott also firing, the home duo’s combined 17-under total was 10 shots clear of the second-placed United States, the defending champions. Denmark and Japan tied for third.
Lahiri placed 25th
Meanwhile, India’s debutants at the World Cup left Royal Melbourne with mixed results and experiences yesterday but vowed to make a quick return to the prestigious event.
Anirban Lahiri emerged the best performer with a final round of one-over-par 72 in blustery conditions to earn a commendable tied 25th finish alongside the likes of Major champion Vijay Singh of Fiji and Europe’s Ryder Cup star Nicholas Colsaerts on three-over-par 287.