The Danny O’Brien-trained filly Shamrocker has overtaken Brazilian Pulse as the favourite to win Saturday’s $550,000 Group 1 Australian Oaks (2400m) after her smart victory in the AJC Derby on the weekend.

Shamrocker ran a close second to Brazilian Pulse in the Group 1 Crown Oaks (2500m) last spring, but has surpassed her in the Australian Oaks odds after beating home the boys in the $1.5 million Australian Derby (2400m) at Randwick last Saturday.

The win came just two starts after the daughter of O’Reilly claimed an upset victory in the Group 1 Australian Guineas (1600m) at Flemington on March 5, making Shamrocker the first filly in history to complete the unique Australian Guineas / Australian Derby double.

She is now out to make history again as the first horse since Research in 1989 to take out the Australian Derby / Australian Oaks double.

Bookmakers have Shamrocker as the $2.80 favourite ahead of Brazilian Pulse at $3.70 in the early markets that feature 94 fillies vying for a spot in the capacity 18-starter Australian Oaks field.

Saturday will be the first time Shamrocker has faced the Michael Moroney-trained Brazilian Pulse since her defeat in the Crown Oaks.

This season Brazilian Pulse has also shown nice form having run second to Do Ra Mi in the Group 2 Kewney Stakes (1400m) first-up on March 12 before winning the Group 3 Keith F Nolan Classic (1800m) at Rosehill and then most recently finished third as the beaten favourite in the Group 1 Vinery Stud Stakes (2000m) on Golden Slipper Day.

There are just two other fillies at single-figure with Fibrillation ($8.50) and Mirjulisa Lass ($9).

Tim Martin’s Diatribe filly Fibrillation ran second to Brazilian Pulse in the Keith F Nolan Classic and then beat her when second to Mirjulisa Lass in the Vinery Stud Stakes.

Rosehill-based trainer Martin said his grey filly would be hard to beat if the Oaks is run on a rain-affected track on Saturday.

“My filly loves it wet and if those conditions prevail in the Oaks, she is going to be very hard to hold out,” Martin said.

“At the moment there are two things that worry me, one is a firm track and the other is Shamrocker.

“However, my filly is fighting fit for Saturday and Damien Oliver has been booked for the ride.”

Prepared by Gregory Hickman, Danasinga filly Mirjulisa Lass went out as a $51 roughie in the Vinery Stud before storming into Oaks contention with her impressive two and a half length success.

A longer-priced Australian Oaks hopeful that ran the ideal prep last Saturday is the Ron Quinton-trained Crafty Irna.

The daughter of Starcraft scored an upset win in the Group 3 Adrian Knox Stakes (2000m) on Derby Day, but the bookies have seemingly ignored that form and she remains a $26 outsider in the Oaks markets.

Quinton, a former champion jockey, rode three AJC Oaks winners throughout his career as a hoop and has further Oaks experience having also prepared VRC Oaks winner Bulla Borghese in 2002.

“She’s worthy of taking her place in an Oaks field,” Quinton said of Crafty Irna.

“In fact she’s going into the race off a similar preparation as Bulla Borghese had.

“Her lead-in run was over 2000 metres and it’s been the same with Crafty Irna.

“Really, Crafty Irna has just trained on beautifully this preparation. Everything has been like clockwork.”

Quinton, however, is not overly bullish having to face Shamrocker on Saturday.

“The Derby winner (Shamrocker) is entitled to be favourite and she will be very, very hard to beat,” he said.

“But my filly won’t be out of place because she’s bred to stay and there was a lot I liked about her win on Saturday.”

Acceptances for the 2011 Patinack Farm Australian Oaks will be released tomorrow, Wednesday April 13, and published right here a Races.com.au.