Gai Waterhouse's hopes of a first Cox Plate victory have strengthened with the news Atlantic Jewel will miss the spring carnival.

The Mark Kavanagh-trained Atlantic Jewel, the early favourite, has been ruled out of the spring with a tendon issue, robbing the carnival of one of its headline acts.

Waterhouse sympathised with Kavanagh as her stable stars More Joyous and Pierro were promoted to first and second favouritism.

Star mare More Joyous is at $6 with TAB Sportsbet ahead of her three-year-old stablemate Pierro at $7.

"You don't like any good horse being ruled out," Waterhouse said at Canterbury on Wednesday.

"The spring is such an exciting time for racing in Australia, we are so much under the microscope.

"Coolmore are such huge owners and breeders, they would be terribly disappointed and so would her trainer Mark Kavanagh. He would be devastated."

Eight-time Group One winner More Joyous won a barrier trial at Randwick on Monday and Waterhouse said she was looking at a return race next month.

"She will probably start off in the Sheraco Stakes," Waterhouse said.

With More Joyous and Pierro now at the top of a revised Cox Plate market, the trainer said she was looking forward to the spring having dominated the Sydney autumn.

"These are very exciting horses at two different ends of the spectrum. The older mare (More Joyous) against the young buck (Pierro)," she said.

Waterhouse is hoping to secure Craig Williams for the Cox Plate ride on Pierro and expects the star jockey to make a decision after Pierro makes his spring return.

Atlantic Jewel is unbeaten in her seven starts including Group One wins in last year's Thousand Guineas and the weight-for-age All Aged Stakes during this year's autumn carnival.

Kavanagh said the star four-year-old was found to be lame following a gallop on Tuesday morning with subsequent scans revealing she had injured a tendon.

"We will continue to assess the injury and it would be my opinion at this stage that she will be unable to resume full training for eight weeks," Kavanagh told Racing Victoria.

"It may be the end of the spring, but it's not the end of the horse."