Sea Moon faces a spring carnival moment of truth on Saturday with jockey Brett Prebble hoping the highly-rated import brings his European form to Flemington.

Sea Moon steps up in distance in the Listed Bart Cummings (2520m) which Prebble believes gives the horse his chance to shine.

Prebble says Sea Moon, one of prominent owner Lloyd Williams' string of European stayers, needs to live up to his high ranking to prove he is a genuine contender for this year's Melbourne Cup.

"If he doesn't, he's not. That's the bottom line," Prebble said.

"He's got to show his form now. I think the boss will be very disappointed with the horse if he doesn't show his true form on the weekend.

"The 2500 (metres) is really going to be the big key thing for him in showing his ability."

Sea Moon has finished back in the field in two starts so far in Australia.

He sprawled coming out of the barriers first-up in the Makybe Diva Stakes (1600m) which damaged his chances and Prebble said he was unsuited by a slowly-run, on-speed dominated Underwood Stakes (1800m) last start when 13th, five lengths behind the winner It's A Dundeel.

Prebble is yet to ride Sea Moon in a race but said the entire, winner of last year's Group Two Hardwicke Stakes (2414m) at Royal Ascot, had given him a great feeling in two exhibition gallops before his Australian debut.

"He's obviously got a very big engine and he's a high-class horse," the jockey said.

"We haven't had the privilege of seeing him perform in a race like that yet (in Australia), but now he's at a distance that's suitable.

"It's a handicap so he's got topweight (60kg) but the weights are pretty compressed so he's not too badly off.

"The 2500 metres is a plus so I'm looking forward to getting on him and I'd like everyone to see him if he lets go and shows that true form."

Sea Moon is the $2.70 favourite while stablemate Tanby is out to go back-to-back in the race and is on the fourth line of betting at $9.