Trainer Pat Carey has already snared one time-honoured Classic at Randwick with a maiden and is back to try for another with a sister to his Derby winner Ethiopia.

But this one is likely to prove a more difficult task.

Carey produced Ethiopia to win the 2012 Australian Derby as a maiden at his fourth start while his sister Blue Eyes will take her place in Saturday's ATC Oaks as one of the outsiders at her fifth start.

Ethiopia scored as a $15 chance on the back of stakes placings in the Autumn Classic and Alister Clark Stakes, while Blue Eyes is at $101 in TAB betting having finished 10th in last week's Adrian Knox Stakes.

Carey has won a VRC Oaks with Arapaho Miss and Queensland Oaks with Gondokoro and is happy to give Blue Eyes her chance.

"Ethiopia was going in (to the Derby) off the back of two stakes performances in Melbourne including the Alister Clark where he ran second and probably should have nearly won," Carey said.

"He should have nearly been going in as a last-start winner, so her (Blue Eyes) form hasn't been of that standard but we feel she is an improving type and we're going to give her her chance."

The filly gets her name because she has the blue eyes common to many horses with white blazes.

Carey said it was hard to assess Blue Eyes on the Adrian Knox run because she settled back on the wet track and failed to make an impact from where she was.