The step up from midweek class to a Saturday race containing seven last-start winners would normally be a significant obstacle for a young horse.

But Pat Carey believes the circumstances surrounding the win of his filly Donna Madeira at Sandown last Wednesday week are far from normal.

Donna Madeira is one of the seven fillies who bring winning form into their division of Saturday's Blue Diamond Previews, and in Carey's opinion, hers is no less worthy than that of her rivals.

Donna Madeira ran a course record of 51.4 seconds for 900m on debut at Sandown, but Carey isn't placing too much emphasis on the overall time.

"She ran a record, but they don't have many 900-metre races at Sandown," Carey siad.

"What was more impressive were her sectionals, they were some of the best for the day.

"To me, that's what made it a very good effort."

After a slick opening 300m which set up a clear lead, Donna Madeira ran her final 600m in 33.1 seconds to easily beat the heavily-backed John Sadler-trained Sworn Revenge.

"If the second horse had won, they'd be talking about her as a Blue Diamond chance," Carey said.

"We beat her by nearly two lengths, so we're entitled to be spoken about as well."

Among the 10 runners in the fillies' Preview (1000m) are Blue Diamond favourite Miracles Of Life, an impressive winner at her only two starts in Adelaide, the Peter Snowden-trained Montsegur, a Caulfield winner at her only appearance and the Peter Moody pair Diamond Glow and Mystical Miss who have both won at their only appearances.

But Carey sees nothing in their form that he hasn't observed in Donna Madeira.

"Probably the only trainer in the race who can make a good comparison is Peter Snowden because he's got a lot of young ones with exposed form," he said.

"But I know my filly shows a lot of maturity, she's race-smart and she's got a lot of speed.

"And one of the biggest things is that she's very sound.

"Most of these young horses have growing pains or sore shins.

"It's unusual if they don't, so that's something in our favour."

In a more open colts and geldings division of the Previews, the Moody-trained Thermal Current is the $3 favourite ahead of Kuroshio.