Swimming with Klim, Fydler and Ian Thorpe, the Australians were not expected to win, as the United States had never lost the event at Olympic level.

The following year, 2002 saw his finest moment as he won individual gold at the 2002 World Short Course Championships in Moscow, Russia in the 100 m freestyle.

However, at the Athens Olympics, Callus swum much slower in the heats of his individual events and was a long margin from even qualifying for the semi-finals.

At the 2008 Summer Olympics, Callus was part of the Australian 4 × 100 m freestyle relay team, which won the bronze medal in the event.

Callus made a return in 2009 at the Aus trials, despite clocking thunderous times in the prelims and semi-finals, he failed to beat the younger generation of sprinters in Eamon Sullivan & Matthew Abood.

In a post swim interview he claimed due to the slow real estate market he had more free time to return to the pool.