Prepared by Tony McEvoy, Game Keeper had the benefit of race experience having finished a close fourth at his first two starts at Geelong and Flemington.
Sent to the front in this 1200 metre assignment, he led all the way with Conqueror a gallant second beaten three quarters of a length.
"It was good to see him keep fighting like that," said stable representative Darren McLeod.
"The last two starts he's been up against it, but today he had the advantage of race experience.
"He can be quite colty, so we have to keep his mind on the job."
A $175,000 Magic Millions purchase for McEvoy Mitchell Racing from the Coolmore draft, Game Keeper is the third winner from multiple Group II winning filly My Tusker, a grand-daughter of champion New Zealand mare Horlicks, whose family has produced Group I stars Brew, Fiumicino and Sacred Elixir.
Coolmore will offer the current yearling from My Tusker, a filly by Pierro, at the Inglis Classic next week as Lot 553.