With six horses in work, Bryce Heys wants to make sure exciting sprinter Spieth and his little brother Travancore have every possible chance to win at their first outings in Listed company.
The 30-year-old trainer will wait until the barrier daw for Saturday's Lightning at Randwick over 1100m before deciding whether to accept with Spieth.
"I'm not going to run him if he draws the outside," Heys said.
If Spieth runs, it will be his first start since he was sent down the Flemington straight in a three-year-old open handicap in June with an eye to education.
He won despite making mistakes, flagging his future potential.
The now four-year-old's physical development has shown his transformation from colt to stallion, Heys said.
"He's always been a large horse but naturally with any horse, three to four is when they really are coming into their adult years," he said.
Spieth holds a nomination for the Group One Darley Classic (1200m) on the final day of the Melbourne Cup Carnival.
Other straight-track options at Flemington include the Group Two Linlithgow Stakes (1200m) on Derby Day.
But Heys is reluctant to earmark a target until Spieth proves he deserves a trip to Melbourne.
"If he can't run in the first three on Saturday there's no point going south," Heys said.
And he is confident the horse will prove himself in the Lightning.
"I was desperate to run him over 1100 metres first-up and I think it's a natural step up for him," Heys said.
"It will be a tough race but it's a natural step and a step that he can take."
Spieth has opened the $4.60 favourite in the TAB's early market with the Hawkes Racing-trained Kaepernick and Gerald Ryan-trained Kinglike sharing the second line of betting at $6.
Boss Lane, Brook Road, Inz'N'Out and Sarajevo are all at $11.
Heys said Spieth's half-brother Travancore would also need to draw a decent barrier to take his place in the Listed Brian Crowley Stakes.
Travancore dug deep to win a maiden at Newcastle at his second start on August 27.
"He's still a bit new and raw and I don't know if he's a top level horse but he'll be a nice horse next year," Heys said.
"He'll definitely be a Brisbane winter horse."
It will be a tough step up in grade for Travancore, with El Divino, Guard Of Honour and Hair Trigger among the 17 nominations.