Star Surprise faces a test of his sprinting credentials in the Vain Stakes at Caulfield, with trainer Mike Moroney interested to see how the gelding measures up against some well-performed colts over a suitable distance.

Saturday's Group Three Vain (1100m) for three-year-old colts and geldings had 15 nominations but a field of eight has been declared which is headlined by Dubious and Bivouac who both won at Group level during their juvenile seasons.

Bought for $8000 by Moroney's brother Paul as a yearling, Star Surprise has won two of his three starts including a city win at Caulfield last month over 1200m to earn his chance in the Vain at the same track.

"I've always had an opinion of him and he is a sprinter, so this is his right race," Moroney said.

"If he's going to be up to the better ones, this will be his right race."

Moroney says while Star Surprise is only small, he has shown ability.

"He has always been a natural," he said.

"I said to Paul right from day dot he could really gallop.

"And he's a competitor. Every time he goes out there he puts his heart and soul into it.

"He has had a month between runs but he did that last time and he seemed to handle it when he won at Caulfield."

Moroney admits it is a big step up for Star Surprise coming through winter races to now clashing with the likes of dual Group winner Dubious.

Bivouac, who has been installed the early $2.70 favourite over Dubious at $3.50, is also coming off a Kindergarten Stakes win at his most recent start in Sydney in April.

Star Surprise, to be ridden by Kerrin McEvoy, was on the fourth line of betting on Wednesday at $8.