In a day of ups and downs for international visitors to the Melbourne spring carnival, Caulfield Cup favourite Yucatan will not run in the race.

The winner of Saturday's Herbert Power Stakes is trained by Aidan O'Brien for six-time Melbourne Cup-winning owner Lloyd Williams.

The Herbert Power win guaranteed the Irish horse a berth in Saturday's Caulfield Cup with 52kg and by Monday morning he was favourite.

In the afternoon, Racing Victoria's chief handicapper Greg Carpenter announced Yucatan had been penalised 2.5kg to 54.5kg for the Melbourne Cup, moving him up the order of entry and safely in the field.

The Chris Waller-trained Youngstar is the TAB's new $5.50 Caulfield Cup favourite while Yucatan is at the head of the Melbourne Cup market at $9 alongside Avilius who is trained in Australia by James Cummings.

Visiting English Godolphin horse Emotionless, trained by Charlie Appleby, has been diagnosed with a fracture in his pelvis and will returrn home as soon as he is cleared to travel.

The Appleby-trained Cross Counter has suffered a cut leg which the stable is managing in a bid to get him to the Melbourne Cup.

Williams could still have two Caulfield Cup runners, the O'Brien-trained The Cliffsofmoher and Homesman prepared by the owner's private trainer, Liam Howley.