Craig Williams is uncertain where Volkstok'n'barrell sits against the best middle-distance gallopers in Australia.

But he expects to have a clearer guide after the Underwood Stakes at Caulfield on Saturday.

While Williams has confidence in Volkstok'n'barrell after winning the Rosehill Guineas on the New Zealander, his one spring ride on the four-year-old raised more questions than answers.

The four-time Victorian jockeys' premiership winner was riding in Japan when Volkstok'n'barrell had his first-up run in the Memsie Stakes at Caulfield on August 29, finishing seventh behind Boban.

Williams returned to the saddle but didn't get a guide as to how the gelding is going when finishing last behind Fawkner in the Makybe Diva Stakes at Flemington on September 12.

After drawing poorly, Williams elected to go forward on Volkstok'n'barrell, sitting just behind the pace.

But at a vital stage in the straight, Volkstok'n'barrell was unable to quicken and take advantage of a gap and went to the finish under a hold, beaten under four lengths.

"I felt inside the last 200 (metres), when I wasn't able to test him, I felt I had plenty of horse to offer," Williams said.

"Since then I've worked him again and I'm happy with his progression.

"It is a cracking field but the horse has come on and he's drawn a lot more favourably this time and will be right in the finish."

Saturday's Underwood has been described as a defining race for connections as the galloper heads towards either a Caulfield Cup or Cox Plate start.

And Williams knows it won't be an easy task with Fawkner and Contributer, two stars he has labelled as the best weight-for-age horses in Australia when right, engaged in the Underwood.

Damien Oliver takes the ride again on Fawkner after guiding him to success at Flemington last time out.

The champion rider said this year's race had depth to it.

"There wasn't a lot between the whole field last time in the Makybe Diva and you would expect a good finish again," Oliver said.

"The Cleaner will be out there making it all from the front and we'll all be trying to run him down.

"My horse, he's drawn well. He's a really consistent horse and rarely puts in a bad one so I'm sure he's going to be right there again."