The $2 million Australian Derby is the aim for the Mark Newnham-trained Righteous Mate but the gelding needs to show he's on target when he runs in the Tulloch Stakes.

Righteous Mate was runner-up to Anaheim in a Listed 1800m race at Flemington at his third career start last spring with that colt fourth in last Saturday's Group One Rosehill Guineas.

Newnham, who is in his first full season as a trainer, had his first Golden Slipper runner last Saturday with seventh-placed Diamond Tathagata.

Righteous Mate steps up to 2000m for the third start of his campaign on Saturday at Rosehill and if he performs well, he will back up a week later over 2400m in the Derby.

He has been unplaced over 1600m in his two lead-up runs, including a benchmark race on heavy going at Warwick Farm last start.

"He's needed the two runs back and the aim has always been to get him to the Derby," Newnham said.

"I'm not sure how well he handles the wet ground, but he'll appreciate the step up in distance anyway and he needs this run to top him off for the following week."

Newnham said if he felt Righteous Mate wasn't up to the Australian Derby after the Tulloch he could change plans and target another Classic interstate.

"He's got to show enough on Saturday to warrant running in the Derby," he said.

"If I think it's only the ground and we're looking at a good track on Derby day we can press on, but if I think he's not quite up to it we could look at Adelaide."

The Group One South Australian Derby is run over 2500m in May.

Righteous Mate is at $12 for the Tulloch Stakes, with the track rated in the heaviest range on Thursday.

Newnham has been happy with how the gelding has been going and said he had come on since his most recent start.

"He keeps improving week to week but we're getting to the business end now so he's got to," he said.