A defining week in the training career of John O'Shea could also prove to be a significant turning point for his smart sprinter Shelford.

O'Shea was this week announced as the replacement for Darley head trainer Peter Snowden who will relinquish the prized post at the end of the Sydney autumn carnival.

Before taking over the Darley reins in May, O'Shea will lead a strong team of his own through the autumn carnival, spearheaded by undefeated mare White Sage and Moonee Valley Vase winner Savvy Nature.

"It's exciting. There are no negatives there," O'Shea said of the Darley job.

"My own team has also got a lot of depth to it and I will be looking to take them right the way through (the autumn)."

One of O'Shea's selling points for the Darley job was surely his ability to shape and guide a stallion prospect and Shelford is his latest assignment.

A well-bred son of Redoute's Choice, the four-year-old was Group placed behind Pierro in the 2012 Todman Stakes and if successful in Saturday's Rosehill Gardens Handicap (1200m) he will be given a shot at Group One success in the Railway Stakes.

"If he wins on Saturday he will probably go over to New Zealand and run in the Group One there on New Year's day," O'Shea said.

"He's just had a freshen up and a nice trial. He's going very well at home."

O'Shea will saddle up Magic Millions carnival hopeful Carmine King in the same race and reported he would strip fitter for his first-up run.

Stablemate Gangster's Choice will resume in the ATC Membership On Sale Now Handicap (1400m) and has drawn the inside alley in his quest to enhance an already handy first-up record.

"He gets a great chance to box seat on a track he races well at on a surface he races well on," O'Shea said.

A duffer on rain-affected ground, Gangster's Choice should get his preferred firm conditions at Rosehill.