In the celebration after his two-stroke victory over Thomas Bjorn, the 26-year-old Queensland native donned a green-and-gold cap, Australia's national colors. But he easily could have been attired in the blue, red, yellow and white of the Philippines.
Day, who is half-Filipino, had perhaps the biggest day of his career less than two weeks after learning that eight of his relatives, including his maternal grandmother, had perished during Typhoon Haiyan, which began to ravage the island country of nearly 100 million people in southeast Asia on Nov. 8.
"It would have been the easiest thing for me to just go ahead and pull out of the tournament with what has been going on over the last week," Day said on Sunday after shooting a final-round 70. "But I really wanted to come down here and play."
Earlier in the week, Day admitted that while he represented Australia in the World Cup, he also was playing for his mother's home country.
"I know that there are guys from the Philippines here and they have got a heavy heart right now for their people," Day said of Angelo Que and Tony Lascuna, who finished in ties for 46th and 50th, respectively. "For me, being half-Australian, half-Filipino, after something like that happens, you tend toward that way."
Over the years, as the world has endured a litany of tragedies, sporting events have eased the burden for hurting people and imbued athletes with a greater sense of purpose. These megastars have the good fortune and power to lift spirits and hearts with great performances on the field of play.
Day, who had only one victory on a major pro tour coming into the World Cup, was seemingly on a mission with his spirited shot-making in Melbourne to prevail over the despair that enveloped much of the Philippines.
He couldn't bring back his grandmother and relatives or the thousands of people who lost their lives to the storm, but he could bear witness to the resiliency of the human spirit.
Sometimes our athletes and sports organizations are called to be more than just performers -- engines for the vast multibillion dollar sports industrial complex that impacts nearly every corner of the known world.
Tragedy demands a response from all of us. And invariably tragedy will confront the sports world with complex dilemmas when the front-page news section makes a quick jump to the sports page.
Fifty years ago, Pete Rozelle made the difficult decision to go ahead with the NFL schedule in the aftermath of the assassination of President John F. Kennedy. Years later, Rozelle would call that choice one of the biggest mistakes of his career.
Yet for many, those football games provided an important escape and a reason to believe in the efficacy of the American ideal of the pursuit of happiness during one of the scariest times in the country's history.
At the 1972 Munich Olympic Games, Avery Brundage, the head of the International Olympic Committee, famously said, "the games must go on" after 11 Israeli athletes were killed by a Palestinian terrorist group.
Brundage's statement was an important message to the terrorists and to the world that not even violence of this magnitude could quench the urgency of the Olympic movement.
The 1989 World Series between the Oakland A's and the San Francisco Giants had a 10-day disruption after an earthquake rocked the Bay Area. That World Series is less remembered for the A's four-game sweep than it is for how the earthquake began less than a half hour before the start of Game 3 at Candlestick Park in San Francisco.
Yet amid the images of the cracks in the roads and stranded motorists, there is one of joyous A's closer Dennis Eckersley being swarmed by his teammates around the pitcher's mound after the final out in the series-clinching Game 4.
The 2012 New York City Marathon was canceled after Hurricane Sandy, but that event reemerged this year with renewed vigor to be the biggest race of its kind in the world.
According to the most recent estimates by the National Disaster Risk Reduction and Management Council, the death toll from Typhoon Haiyan has climbed to over 5,235, and 3.4 million people have been displaced.
It could take years for a full accounting of the devastation wrought by this super typhoon. Nothing short of billions in aid from around the world will restore the central Philippines to what it was prior to the storms.
Day will watch with the rest of the world as this sad story continues to unfold. He has said he will contribute a portion of his $1.5 million first prize toward the relief effort.
Yet in his own way as an athlete on a big stage, the rising PGA Tour star has already done a great service to the relief efforts in the Philippines by embodying the pain and the courage of his people through his excellent play in the World Cup.
Australia might have earned a World Cup, but the Philippines got a new national hero.