Group One-winning sprinter Mrs Onassis will be striving to become just the third mare in the past 20 years to win the first Group race of the season in Sydney when she heads to Randwick on Saturday.

A field of eight has been assembled for the Group Three Missile Stakes (1200m), headed by outstanding gallopers Hay List and Rain Affair.

Mrs Onassis is the only mare in the field and will be attempting to become the first to upstage the males since Pompeii was successful in 2003.

Prior to that mare's victory, the last of the females to win had been Klokka who notched back-to-back victories in 1993-94.

Mrs Onassis will also be attempting to win beyond 1100 metres for the first time.

Luckily for trainer Gerald Ryan, he is not one to dwell on statistics.

"Statistics are only what you want to make them," Ryan said.

"The last time she ran over 1200 was in the Sapphire Stakes (in April) and she never got a crack at them anywhere.

"She's never won at 1200 but now she's an older mare she is racing a bit more relaxed."

In her three runs since she claimed the Group One Oakleigh Plate at Caulfield in March, Mrs Onassis has not managed a place.

But trainer Gerald Ryan says unsuitable tracks and bad luck have been behind her failings.

Mrs Onassis beat just one rival home when she resumed in the Sir John Monash Stakes at Caulfield last month.

Ryan had been bullish about her chances in the lead-up to the race, only to have his hopes quashed by jockey Brenton Avdulla on race morning.

"He walked the track that morning and then he rang me up and said the track wouldn't suit her," Ryan said.

"He thought it was worse than the dead five it was rated that day."

Mrs Onassis' best form has been on firm ground and Ryan is hoping Randwick presents that way on Saturday.

With Avdulla suspended, Oakleigh Plate-winning rider Kerrin McEvoy will be reunited with Mrs Onassis.

"She should get a gun run third or fourth behind the leaders and she's got a Group One jockey on," Ryan said.

"Hopefully the weather stays the same and the track doesn't get any worse."