A week after It's A Dundeel's scintillating Derby win, another three-year-old star will step out at Randwick as the dominant favourite in a major race.

On Saturday it will be Pierro, bidding to extend his unbeaten Sydney record in what is regarded as the toughest 1600m race in the country, the Doncaster Mile.

Victory could set up a mouth watering clash with triple crown winner It's A Dundeel on April 27 over 2000 metres in the weight-for-age Queen Elizabeth Stakes.

Although Pierro is the $2 Doncaster favourite, there are others with claims to lower his colours.

Trainer Guy Walter is hoping he can gain an edge by engaging the most successful Doncaster rider ever, Glen Boss, for Streama who is a $21 chance.

She is one of two runners for Walter with Appearance the more favoured. The triple Group One winner is owned by Sheikh Mohammed's Darley Australia and will be ridden by Kerrin McEvoy.

While Boss holds the record for Doncaster winners with five, Walter has his own piece of race history, training the trifecta in 2005 when Patezza beat Boss's mount Court's In Session with Danni Martine third.

"Both mares are well although it will be a hard race," Walter said.

"Appearance has had a great campaign and Streama ran an improved race last time."

The winner of the Myer Classic in the spring, Appearance has won Sydney's two Group One mares' races at her past two starts, the Coolmore Classic and the Queen Of The Turf.

Streama ran an improved third in the Queen Of The Turf with her jockey Hugh Bowman much talked about for the way he kept the overwhelming favourite More Joyous in a pocket, bringing about her downfall.

Streama carries 52.5kg in the Doncaster, well under Bowman's weight range and also too light for Blake Shinn who claimed a stakes double for the stable on Saturday - the Carbine Club Stakes on Toydini and the Doncaster Prelude on Skyerush who was not a Doncaster entry.

The Bart Cummings-trained Norzita, who finished third in the Coolmore, is the $8 second favourite for the Doncaster while Appearance is a $15 chance.

A natural lightweight, Boss has won the Doncaster on Triple Honour (2008), Haradasun (2007), Racing To Win (2006), Private Steer (2004) and Sprint By (1996).