Now 11, Coole Cody has had 13 of his last 14 outings at the home of National Hunt racing, enjoying plenty of success.
He won the corresponding race in 2020, was going well when falling two out 12 months ago, returned a month later to win the December Gold Cup and then landed the Plate at the Festival in typically buccaneering style.
However, off a mark of 151, Williams believes he faces the toughest ask of his career.
"It's a case of horses for courses with him, it's the oldest saying in the book," said Williams.
"He can't keep winning, can he. With all due respect he ran the other day over hurdles and the handicapper didn't even drop him 1lb.
"Listen, that's the way it is, that's the way the cookie crumbles. I don't think the handicapper will allow him to win another and that is the truth of the matter.
"He's genuine, 100 per cent, he's fit and well and in great form, he's a joy, but even 1lb lower would be a help. He won't mind what the ground is, it's Cheltenham and we'll be running."
Williams also has an entry in Sunday's Unibet Greatwood Hurdle, but the participation of Current Mood is not as certain.
"I'd just like to see a drop of rain for her, she'd need cut in the ground, she'd need it softer than good to soft," said Williams.
"I want to run her, if she's good enough I don't know, but I want to see her in a decent two-mile handicap with cut in the ground as her stamina will come into play and she might run well. She's a very honest mare.
"There's no real standout in the Greatwood this year, that's how I see it, unless I'm missing something, so with the prize-money on offer we have to keep an eye on it."