Detonator Jack exploded to victory in the $1 million Illawarra Mercury Gong feature race at Kembla Grange on Saturday.
Loch Eagle ran a good second ahead of the fast-finishing pre-race favourite Osipenko.
James McDonald, Australia's top jockey, was hoping to sign-off for spring with a victory aboard Osipenko before heading to Hong Kong for a five-week stint but the Chris Waller-trained star had to settle for third.
It was Detonator Jack's day in the 1600m The Gong, with a lovely run midfield before exploding at the right time and proving far too good for his rivals.
Loch Eagle also ran a terrific race and Osipenko got within striking distance but jockey Jason Collett did well to guide Detonator Jack to a relatively comfortable win in a time of 1.36.70 on the heavy track.
Collett was ecstatic with the performance of the Ciaron Maher and David Eustace-trained horse.
"It felt great. He just had a lovely spot," the jockey said of Detonator Jack.
"Loch Eagle tried to drag him and expose him but he was on it today..
"The blinkers helped. When I asked him to be there he was there.
"He was probably aided by the soft ground too.
"But it's a long straight, I got run down earlier and I though I'm here a long way out but he's a powerful horse and he had enough in the tank."
Collett also praised Detonator Jack's acceleration during the race.
"It obviously looked really good, it definitely felt good out there. He has appreciated a couple of slow-run races and probably getting used to the Sydney weight too, so very good."
Meantime local hope Cuban Royale did well to finish in sixth-spot.
In the other main race at Kembla Grange, Insurrection romped to victory in The Warra ahead of Quick Tempo, with Recommendation placing third.
Zac Lloyd rode Insurrection perfectly, leading from start to finish.
Sophie Johnson from Freedman Racing stable said Insurrection had "a big character and a big heart".
"he has paired up well with Zac [Lloyd] and it was nice to get them together again. He is a super little horse," she said.
"He knows his job, he has got a big character and a big heart and he absolutely thrives on the work."