The New Zealand challenge for the Randwick Guineas has been brought unstuck by one of their own with Jim Cassidy producing a masterful ride on Dissident to beat El Roca in the Group One feature.

A proud kiwi but domiciled in Australia for 30 years, Cassidy coaxed everything out of the Peter Moody-trained colt to get him home a short head in front of the favourite at Randwick on Saturday.

Eurozone worked into third, another length away with Atlante and Show The World sixth and 12th respectively for New Zealand trainer Murray Baker.

Dissident's victory put the Moody stable back on the Sydney Group One winners' stage, almost a year since Black Caviar won the TJ Smith Stakes.

"They are a couple of warriors together, a young one and an old one," Moody said of his colt and Cassidy.

"He's toughed it out and he's just got that little bit fitter.

"We saw his efforts here in the spring around Zoustar. He was wide, he had a hard run in the Golden Rose, just got nutted and was probably over the top."

Dissident won the Hobartville Stakes in the absence of El Roca who was a raceday scratching and backed up in the Guineas from his second to Terravista in the Liverpool City Cup a week ago.

Backed from $4.80 to $3.20, El Roca edged past Dissident inside the final 100 metres but shifted in noticeably in few metres and running second probably saved a protest hearing.

"He ran well and maybe having to back up told on him," co-trainer Natalie Young said.

"We might have lost on protest. He did shift in and bump the other horse."

Senior steward Greg Rudolph agreed and said it was a noticeable bump."

El Roca is now likely to head to the weight-for-age George Ryder Stakes (1500m) in two weeks but Moody's sights are firmly on the Rosehill Guineas (2000m) on the same day.

"We go to the Rosehill Guineas which is the race I've always had earmarked and then it'll be decision time, whether we go into the Derby or the Doncaster," Moody said.

"He deserves the Group One win. He's been at the top level his whole way through and it is certainly very fitting on his resume."

Moody paid credit to an emotional Claire Cunningham who looks after the Sydney stable for the Melbourne-based Moody.

"Claire's done a tremendous job," he said. "It's a credit to her and her staff."

Cassidy's availability was a bonus for Moody.

"I was looking for a rider who could stick with him and they don't come any better do they?" he said.

"And no one knows their way around these places better than him. Job done."