The filly showed a professionalism beyond her experience in Saturday's 2YO Handicap (1100m) to make her way through a gap in the straight and power to the line.
Favourite Krameric ($3.50) was on pace early before ending up sixth, four lengths from the winner.
“That was a ripping debut from a very uncomplicated filly,” trainer James Cummings said.
“She has a wonderful attitude. She's not robust like some of the colts we saw in the yard that's for sure.
“She sweated on a run for half a furlong and it didn't faze her. Her attitude is her greatest strength, and when the gap came she sprinted quickly
“I think we have just unveiled another good attribute of hers and that is a very powerful turn of foot.”
Like Tassort, a debut winner a week ago and the ruling Golden Slipper favourite, Athiri will be given a short spell with the autumn in mind.
“With a break and this preparation under her belt, I'm sure she will be far better next time,” Cummings said.
“Her natural ability and closing speed, you can't teach that. It's just there. She has shown that today and that is what we have to work with next year.”
The Hawkes Racing-trained Kapajack is a year older than Athiri but was equally impressive in his first start, winning the 1100m-benchmark 78 from a field of older horses.
Starting at $17, Kapajack finished strongly to beat Mister Songman ($4.60) by a short head.