Promising colt D'Argento has given Hugh Bowman the ideal start to his bid to claim the Sydney jockeys' championship at Rosehill, as a luckless Brenton Avdulla watched on after his mount was scratched at the barriers.

Bowman extended his lead to 3-1/2 wins over Avdulla on Saturday when the $1.70 favourite backed up his victory on debut at Newcastle with an impressive win in the two-year-old handicap (1500m).

Avdulla looked from afar after the Gai Waterhouse and Adrian Bott-trained gelding Regal Cannon failed a vet check after rearing up in his stall, to add another setback to the long-time premiership leader's faltering challenge.

D'Argento was arguably destined to score regardless as the grey finished strongly to beat Runaway ($9.50) by a neck.

"He settled perfectly. He's very tractable, especially stepping up to the 1500 (from 1200 metres). It's exactly what you want to see when you're trying to educate a horse," trainer Chris Waller said.

"Where do we head now? My gut tells just back off and wait for the end of the spring."

Waller said there was still plenty of scope for improvement from the son of So You Think.

"He still floats a little bit. He's never been asked to attack the line because he's a horse that's got a lot of ability so you're actually restraining him in the trials and track gallops," he said.

"At Newcastle he was let off the bridle and got a bit lost. Today was only the second time in his life that he's been asked to quicken. That brings natural improvement."