Tea Rose Stakes winner Funstar and runner-up Probabeel have a stranglehold on Flight Stakes betting but rival trainer Jason Coyle is incredulous more trainers are not taking them on.

A field of six fillies will contest Saturday's $500,000 Flight Stakes (1600m) at Randwick and prize money aside, the Group One status of the race will add valuable black-type to the pedigree page of any who can finish in the placings.

Coyle, who saddles up unheralded filly St Covet's Spirit, reckons tackling stakes company with a young, improving horse at this time of year is a no-brainer.

"With a three-year-old spring filly, if you think they've got ability, I think you've got to try them in those better races," Coyle said.

"Given the size of the field there's probably not many people who agree with me.

"They're spring three-year-olds. They've only had the two-year-old season to dictate which are the better horses and anything that's lightly raced or has needed time are still very early in their careers."

St Covet's Spirit is a $23 chance in what is anticipated to be a two-horse race between $1.85 favourite Funstar and New Zealander Probabeel ($2.20).

Coyle's filly contested the Tea Rose, over-racing because of the stop-start tempo and finishing 5-1/2 lengths behind the two fancies, but her previous form was encouraging.

She was strong late first-up behind subsequent stakes winner Just Thinkin' then posted an exceptional maiden win at Canterbury when she came from last and threaded through the field.

Those glimpses of talent have convinced Coyle to give St Covet's Spirit a shot at Saturday's race.

"I don't think you see many horses win a maiden as impressively as she did," Coyle said.

"You don't head in a direction if you don't think a horse has enough ability to be competitive in these races.

"The top two look very hard to beat and based on the race we were in two weeks ago, we've got to find five lengths and do things right to finish with them.

"I still thought her run was OK last start and if she can do those right things hopefully we can cause an upset."