It was the fourth win in a row for the New Zealand-bred gelding, who has now had a total of eight starts for five wins, two placings and A$276,505 in stakes.
The four-year-old jumped from the inside gate on Saturday and enjoyed a comfortable midfield run under Dean Holland, but he appeared to have his chances extinguished when he was badly blocked by the tiring front-runner Nancho, rounding the home turn.
However, So Unusual regathered himself, found clear air and gradually built up his momentum again, reeling in Youth Spirit and surging to victory by half a length.
"He had some unfortunate circumstances there," co-trainer Calvin McEvoy said. "He began well and had a beautiful run throughout the race. Unfortunately something came back in his lap on the turn, and I thought his race was over.
"They don't normally pick themselves up like that – especially a young, green horse. But the way he did, and the tenacity he showed, was the signs of a very good horse. It's turning into a great story for the owners (micro-share syndicators My Racehorse).
"The great quality about this young stayer is he switches off mid-race, and that's going to take him a long way."
Connections are now considering a shot at the A$500,000 Listed Roy Higgins (2600m) at Flemington on March 25, which carries a ballot-free entry into the Gr.1 Melbourne Cup (3200m).
"We're going to give it some thought," McEvoy said. "There's a big ticket available in that race.
"He's still a very young horse, only four, and I have no doubts that he's going to be better next preparation and again in 12 months' time. We want to treat him carefully and treat him with the respect he deserves.
"But if he bounces through today, there's every chance we'll show up in the Roy Higgins."
Bred by Nigel and Adaire Auret, So Unusual was identified by Bloodstock Agent Phill Cataldo.
The progressive stayer is a good advertisement for his Letham Stud-based sire Unusual Suspect, who was the winner of the Gr.1 Hollywood Turf Cup (2400m).