Brett Cavanough originally worked Another Sin in darkness to keep him under wraps.

But there is no avoiding the spotlight at Rosehill on Saturday after a betting plunge which has the unraced gelding favourite for the Highway Handicap.

It is unconventional for a country horse to make its debut in a Highway race, but the Scone trainer is backing his judgment, plus the insight of jockeys who have assessed Another Sin at close quarters.

"I told a couple of owners I think he's sharp enough and smart enough and if he can win four Highways you can get your hands on a couple of hundred thousand," Cavanough said.

The connections needed little convincing and are likely behind the plunge from $14 on the TAB's first market to $4.20 favouritism on Friday.

"They like a punt," Cavanough said.

"He might lose it when he gets in the mounting yard, but he's pretty well-rounded. He's jumped out a lot. I don't think it'll faze him."

Cavanough, who had two maiden winners, Peppermint Patty and Subtle Winner, at Tamworth on Friday, has always had a high opinion of Another Sin but initially maintained a low profile with him, firstly at his Albury base and again when he moved to Scone.

He would work Another Sin in the dark before Brad Clark and Andrew Gibbons were let in on the secret.

"Brad jumped him out on the inner track at Wagga and everyone was all smiles," Cavanough said.

Gibbons then guided him to the post in his solitary trial at Scone on July 24 and reckoned the two-length winning margin could easily have trebled.

"Andrew said he could could have put another four or five on them so we thought we'd have a crack," Cavanough said.