Trainer Alan Hunter knows he's taking a leap into the unknown with $101 debut winner Astro Castro.

A winner over 1100m in three-year-old company at Flemington in July, Astro Castro lines up for his second race in the Group Two Bobbie Lewis Quality on Saturday.

"We're looking forward to it," Hunter said.

"There's no expectations from us, more curiosity I suppose."

Hunter could have taken the easier option of a benchmark 78 race at Sandown on Wednesday, but thought Flemington would give him a better guide to Astro Castro's ability.

Astro Castro is owned by Hunter's uncle, Gavin Burns, and following the debut win the pair fielded some attractive overseas offers.

While they were tempting, Burns decided to keep the four-year-old and if successful on Saturday, would be unlikely to sell.

Hunter said he gave Astro Castro some time off after the Flemington win which allowed him and Burns to evaluate the offers.

"There was a lot of money offered," Hunter said.

"I said to my uncle there is no rush to decide, so we sent him down to a water walker for a week and took a few deep breaths."

Astro Castro galloped before the race meeting at Geelong on Sunday and pleased all concerned.

Hunter says Saturday's race is not ideal but if Astro Castro is the horse he thinks he is, he will be meeting similar opposition in the future.

"We've got to take them on at some stage but then we can come back from that if we have to after Saturday," Hunter said.

"What he did first time down the straight and to finish off like he did, I think that shows he's a smart horse but he's got to go and do it again."

Astro Castro holds a Cox Plate entry, but Hunter says that's probably aiming too high this year.