D'Argento has emphatically answered a distance doubt trainer Chris Waller had on the colt, winning the Rosehill Guineas brilliantly on his home track.

Giving Waller and jockey Hugh Bowman their second Group One win for the day on Saturday after champion Winx's George Ryder Stakes, D'Argento powered home out wide to claim the 2000m race for three-year-olds.

Waller now has a decision whether the bring the colt back in distance for a crack at the $3 million Doncaster Mile - a race the trainer has won six times - or step him up in distance again against his own age in the $2 million Australian Derby (2400m).

Both races are at Randwick in two weeks.

"I had serious doubts about him getting 2000 metres because I've seen the brilliance that he's got," Waller said.

"You don't normally see a brilliant sprinter-miler, that I thought he was prior to the Randwick Guineas where he had no luck, come out and be dominant in the Rosehill Guineas after being three-wide.

"So I've got to re-assess that. He obviously can stay.

"And I've got to work out from a colt's perspective, where's his best value? Is it a Doncaster so he can show off that speed over a mile, or do we go down the Derby path?

"We'll think about everything in the next few days."

Waller ended up with the quinella in Saturday's Guineas when Tangled ($81), who was third across the line, was promoted to second after a protest.

New Zealand Derby winner Vin De Dance ($15) had been second across the line, 1-1/4 lengths behind D'Argento, but was relegated to fourth after a protest from the rider of Furore who had come in fourth.

Stewards upheld Brenton Avdulla's fourth against second protest for interference in the straight, meaning Tangled went to second and Furore ($12) took third.

D'Argento had finished seventh in the Randwick Guineas at his previous start but both Waller and Bowman said the colt had no luck in the race.

Bowman said he had had so much confidence in D'Argento for a long time.

"I always thought 10 furlongs would be his best trip but I'd be inclined to push Chris (Waller) to take him to the Derby after today's performance," Bowman said.

"He really relaxed in the run and he was strong late. Whatever he does this time in he'll be a better horse in the spring. He's still immature."

D'Argento only has 49kg in the Doncaster Mile and firmed from $26 into $11.

He has moved from $7 to $4 favourite for the Derby.