The horse trainer Mike Moroney considers his best chance of a first Caulfield Guineas win begins his campaign towards the feature on Saturday.

The unbeaten Merion resumes in the Listed Mitchell McKenzie Stakes (1200m) at Moonee Valley having come through a similar path to that of last year's Guineas winner Long John.

Merion claimed his maiden at Bendigo over 1300m in late March before adding the Listed Anzac Day Stakes (1410m) at Flemington by half a length.

Long John won the corresponding Bendigo maiden a year earlier and was a dominant winner of the Anzac Day Stakes by almost four lengths at his third start as a juvenile after also winning impressively at Sandown.

The 2013 Mitchell McKenzie Stakes launched the then Peter Snowden-trained Long John's three-year-old spring campaign when he finished third to Cauthen and Shamus Award.

Moroney is excited about Merion's prospects and believes he has the talent to be a contender in the feature three-year-old races.

"His main aim is going to be the Caulfield Guineas and then we'll just take it from there as to whether we go a bit further," Moroney said.

"He's a lovely horse and he's really matured as well with his break.

"To the eye he looks a better horse."

Saturday's race has attracted 26 nominations with a field limit of 13 plus four emergencies.

Group Two VRC Sires' Produce Stakes runner-up Awesome Rock is nominated to resume as is Divan who finished in a dead-heat for third in the Anzac Day Stakes on debut after coming from near last in the straight.

Merion and Divan are both at $21 for the Caulfield Guineas in October while Awesome Rock is at $31.

Merion has had two jump-outs at Flemington to prepare for his return.

Moroney believes the O'Reilly gelding could find the 1200m around Moonee Valley too short but says it is the right starting point.

"He's bred to get a bit further and Steve (Arnold) said after Friday's jump-out he was starting to feel like 1200 metres is going to be a bit sharp for him," Moroney said.

"He's going to want to get to 1400 metres and a mile pretty quickly."