The potential of lightly-raced filly Isabella Snowflake will be put to the test on Saturday in a Galaxy field jockey Craig Newitt describes as arguably the toughest in a decade.

Despite being without sprint star Hay List, Newitt says the 1100m Rosehill race will still show whether the filly is up to mixing it in Group One company.

"She deserves her chance in a race like this but I think she's a bit stiff to have run into probably the toughest Galaxy in the past 10 years," Newitt said.

The capacity field includes brilliant filly Snitzerland who is favourite coming off a record-breaking Challenge Stakes win.

Triple Group One winner Sea Siren makes her first appearance of the autumn while the past two Galaxy winners, Temple Of Boom and Atomic Force, are also engaged.

"She's struck a pretty hot race but she's very lightly-raced and has no weight on her back," Newitt said of Isabella Snowflake who has won four of her five starts.

"I'm sure she'll give a good sight."

Newitt, who returns from suspension on Saturday, expected Isabella Snowflake to prove too good first-up at Flemington in the Listed Bob Hoysted (1000m) and the filly got the job done, beating Ready To Rip and Karuta Queen.

"She's going to have to improve again going into this but I'm sure she has," Newitt said.

"I expect her to run well and we'll see whether she measures up."

Adding to her task, and that of the favourite, is that only two fillies have won the Galaxy in its 41 runnings.

Another up-and-comer to gain a start is first emergency Unpretentious who has had some support at double figure odds.

The Nikki Burke-trained four-year-old was an impressive winner in Listed company during the Melbourne Cup carnival and has top jockey Craig Williams aboard.

"I've got a lot of time for him," Williams said.

"It's going to be a great Galaxy this year but he should acquit himself well in that field."