Glen Boss isn't unhappy to have linked up with Victoria Derby winner Fiveandahalfstar at Caulfield on Saturday, if only to clarify his thoughts on the form of last spring's staying three-year-olds.

Boss rode Hvasstan into fourth place behind Fiveandahalfstar in the Derby and although he has a good opinion of that colt, he has doubts about the overall quality of the race.

"I think the Derby form is questionable," Boss said.

"It was a funny run race and I just wonder about it."

Fiveandahalfstar meets Hvasstan and a strong group of three-year-olds in the Group Two Autumn Stakes (1400m).

Boss takes over from the disqualified Damien Oliver on Fiveandahalfstar who he rode for the first time in a gallop at Caulfield this week.

While Hvasstan and Fiveandahalfstar are two of the better staying prospects from last spring, Saturday's race has also drawn in the highly-regarded Mick Kent runner High Shot and the Peter Moody-trained Mulaazem.

High Shot won a modest Cranbourne maiden at the only start of his first preparation, but Kent has ambitious plans for the son of High Chaparral that include the Australia Derby at Randwick in April.

"I've had the Australian Derby earmarked for him for a while," Kent said.

High Shot showed he was forward enough to run a good race on Saturday when he finished an outstanding third without being pushed in a Werribee trial on Monday.

He was originally accompanied in the entries for Saturday's race by his stablemate Philippi whose reappearance is now likely to be in next Saturday's CS Hayes Stakes at Flemington.