Stubbs finished in a share of 32nd place at five-over par in his title defence at the Asia-Pacific Amateur Championship in Japan on Sunday.
One of the men Stubbs beat in last year's playoff at Royal Melbourne - China's Wenyi Ding - gained redemption by claiming this year's title with a 12-under par total.
Stubbs and fellow Australian Quinn Croker will now turn professional, with Phoenix Campbell to follow suit shortly after.Â
Stubbs faces 16 hours of flight time to reach Western Australia and the resumption of the 2024/25 Challenger PGA Tour of Australasia.
His first event as a professional is the CKB WA PGA Championship in Kalgoorlie, starting Thursday.
"I never really felt like I could get anything going," the Victorian said of his final tournament as an amateur.
"As soon as I'd make a couple of birdies, I'd give them straight back, and that's how the whole week sort of went.
"It's been a cool week trying to defend. Unfortunately, not the week I was hoping for, but still a special week."
A champion's highlight reel 🎬 — Asia-Pacific Amateur Championship (@AAC_Golf) pic.twitter.com/0TR2X2PhckOctober 6, 2024
Meanwhile, Croker will tackle the first stage of Korn Ferry Tour Qualifying School in Florida in the United States from October 15-18 before taking up the Challenger PGA Tour of Australasia membership he earned by winning the Future Tour category last season.
His first Challenger PGA Tour of Australasia event as a professional will be Webex Players Series South Australia in Willunga.
Campbell finished in a share of 13th at two under in Japan, meaning he ended as the best-placed Australian at the Asia-Pacific Amateur Championship.His victory chances disappeared when he dropped three shots late in the third round.Campbell has just one tournament left to play as an amateur, the Japan Open at Tokyo Golf Club this week, before he too switches over to the professional ranks.The Victorian's debut as a pro will come at the 100th WA Open, starting on October 17 at Mandurah Golf and Country Club.