Williams' and his leviathan owner father Lloyd have brought their Irish-trained stayer Twilight Payment back to defend his title in 'the race that stops the nation', with Williams senior shooting for his eighth win in the race.
"Incentivise is a star, obviously, without sounding like I'm stating the bleating obvious, but he hasn't run two miles yet," Williams said.
"Both our horse and Spanish Mission, they're proven at the distance at the absolute top level in the world, so we'll see on Tuesday whether Incentivise is up to that level at that trip.
"He may well be just too good, or he might not be there, only time will tell."
Williams was at Werribee on Friday morning to oversee the final stages of Twilight Payment's Cup preparation and is pleased with the nine-year-old's condition.
"He looks terrific," he said. "He's a very happy horse and a very fit horse. He looks like he's going to go into the race in great order."
Twilight Payment will lug 2.5kg more this year than what he carried to victory in last year's Cup, but it is a different sort of field to that which he beat 12 months ago.
"It's been unfortunate that we've had some attrition and it's just terrible luck for the people that have had horses go amiss, you wouldn't wish it on anyone with the amount of work that it takes to get a horse to this race," Williams said.
"I feel very sorry for them, having been in that position ourselves, I know exactly how they feel, but anyway, what it is, it's the greatest race in Australia and it doesn't matter who's in it, it will always be the greatest race in Australia."
