Pierro has already cemented his status as one of the best colts of his generation.

But in an ominous sign for his rivals, one of the men who knows him best believes he is a more complete horse this campaign.

Former jockey Mark Newnham, now right-hand man to trainer Gai Waterhouse, rides Pierro in the bulk of his work and even made a recent comeback to partner him in a barrier trial.

He says last year's Golden Slipper winner and Cox Plate placegetter has improved since the spring, physically and mentally.

"He's bigger and stronger," Newnham said.

"I think he has taken another step. He's just a more mature horse."

Unbeaten as a juvenile, Pierro suffered his first defeat in the Caulfield Guineas when he was chased down by All Too Hard after a tough run on the speed.

The two colts showed their mettle when they subsequently filled the minor placings behind Ocean Park in the Cox Plate.

All Too Hard has already returned to win the Orr and Futurity Stakes double in Melbourne and is a short-priced favourite to add Saturday's Australian Guineas at Flemington to his resume.

Pierro will get his first chance to stake a claim for title of Australia's best colt when he resumes in the Group Two Hobartville Stakes (1400m) at Rosehill on Saturday.

He is a resounding favourite at $1.75, ahead of the unbeaten Rebel Dane ($4.60) and his Waterhouse-trained stablemate Proisir ($7.50).

Proisir was runner-up in the Spring Champion Stakes at just his fourth start and wasn't disgraced when eighth in the Cox Plate at his fifth.

Like Pierro, he hasn't raced since the weight-for-age championship but his future looks bright.

However, when it comes to the Hobartville, Newnham echoes the sentiments of punters and says Pierro is the pick of the pair as he is naturally more forward than his chunkier stablemate.

"They're a bit different physically. Proisir is more a heavily-built colt so it's only natural he would take a bit longer to come to his peak," Newnham said.

"I just hope they both finish their campaigns with Group One wins. One has done it and one is promising to do it."

Pierro is undefeated first-up and has never lost a race in Sydney.

He will jump from barrier nine while Proisir has drawn the outside in the field of 11.