Craig Williams's hopes of back-to-back Cox Plate wins fell flat at Moonee Valley on Saturday as favourite Green Moon didn't show the fight the jockey had expected.

Williams won the Cox Plate last year on Pinker Pinker and went into this year's race on Green Moon, a horse he said this week he'd love to go to war with.

But after racing three-wide in the showpiece weight-for-age contest, Williams said Green Moon was beaten a long way from home before finishing seventh.

"I'd just like to see how he pulled up because that's not the horse that I know," Williams said.

"You don't win many weight-for-age races sitting three-wide.

"He did get tightened and buffeted going out of the straight the first time but I didn't have a horse from the 600-metre mark at all.

"(The winner) Ocean Park followed me throughout and when the chips were down I expected my horse to pick up. He tracked a bit sideways around the turn and didn't show his usual guts and determination in today's race."

Green Moon started the $5 favourite ahead of three-year-old Pierro ($5.50) who finished third.