New Zealand raider Aegon dominated at his Australian debut but rival trainer John O'Shea believes the locals won't be such easy pickings in the first leg of Sydney's three-year-old triple crown.

Prepared by master horseman Murray Baker and training partner Andrew Forsman, Aegon showed sparkling acceleration to stretch his unbeaten record to five when he outclassed his rivals in the Hobartville Stakes (1400m) two weeks ago.

The O'Shea-trained Lion's Roar finished fifth and will again face off against Aegon in the Group One Randwick Guineas (1600m) on Saturday.

Aegon has opened a clear-cut +130 favourite with TAB fixed odds but O'Shea expects the Sydney three-year-olds to be much more competitive as they get deeper into their campaigns.

“He (Aegon) was a horse that, on the day, had the right profile. He'd had the run at the mile, he'd had a month between runs, then he got a great (Hugh) Bowman ride,” O'Shea said.

“A lot of the Sydney horses, and ours included, were open to significant improvement going into that run, albeit they have to turn around a significant disadvantage.”

Lion's Roar, a $65,000 Karaka yearling purchase, is a son of Contributer, who O'Shea trained to win back-to-back Group One races for Godolphin during the 2015 Sydney autumn carnival.

The gelding narrowly missed an elite win of his own when he finished second to star filly Montefilia in the Spring Champion Stakes in October.

O'Shea said a wide draw in barrier 10 had made the task harder for Lion's Roar on Saturday but he expected a bold run ahead of the Rosehill Guineas, which will be his target race.

“He is drawn awkwardly in a race where there looks to be an abundance of speed. We would have loved to draw a little softer where we could have maybe got a softer run in transit,” O'Shea said.

“But he's in good order and he's made significant improvement from his last run.”