A second-up disappointment in the spring is playing on the mind of trainer John O'Shea ahead of Contributer's quest for a Group One Chipping Norton Stakes win.

Contributer made a winning Australian debut with a black-type success during the Caulfield Cup carnival but couldn't replicate that performance when midfield in the Emirates Stakes.

But he was again impressive when fresh at Randwick earlier this month and heads to Warwick Farm on Saturday as the $2.80 favourite in early markets.

Bookmakers clearly believe his second-up run in the Emirates was an anomaly but O'Shea is taking a more cautious view.

"It's a valid concern," he said.

"The market would have him top pick and he's probably entitled to be favourite.

"But whether he alleviates the concerns mentioned, I can't say yes or no. All I can say is the preparation has been good."

Contributer could be a landmark horse in O'Shea's career.

The trainer is chasing his first Group One win since taking over Sheikh Mohammed's Australian operation and while he has three chances to achieve that in Melbourne on Saturday, Contributer will race first.

Second-up doubts aside, O'Shea is comfortable the horse is in the right shape to deliver once more.

"We think he's at least held his form or improved a little," O'Shea said.

Contributer's Apollo Stakes win also captured the attention of rival trainers.

Chris Waller, who will saddle up eight of the 15 runners when he chases his fifth consecutive Chipping Norton Stakes victory, all but concedes they will be running for second if Contributer reproduces his first-up effort.

"He's the horse to beat and if he runs like he did the other day he'll win again," Waller said.

At $9.50, Weary is the top pick of Waller's contingent, ahead of stablemates He's Your Man ($10) and last year's winner's Boban ($11).

Caulfield Cup placegetter Lucia Valentina ($5.50) is considered Contributer's danger after coming from second last to finish fourth in the Apollo.

"She's tightened up as we'd hope for off a first-up run," trainer Kris Lees said.