The riding brilliance of Jimmy Cassidy and the training skills of John O'Shea have combined perfectly with the outstanding galloping ability of Sea Siren to claim the Manikato Stakes (1200m) at Moonee Valley.

The winner of both the Doomben 10,000 and BTC Cup in Brisbane, both at Group One during the winter, Sea Siren joined an elite group with Friday's third win at the highest level.

"She deserved it and the ride deserved it," O'Shea said.

Cassidy immediately found the perfect position on Sea Siren, one off the fence outside the favourite Buffering and on the back of joint leader Satin Shoes.

From the 1000m mark, everything went to a script that was written on Tuesday when Sea Siren galloped at Moonee Valley.

"She took the Valley like a duck to water," Cassidy said.

"I knew on the corner they'd have to be good to come from behind me and beat me.

"I thought she'd win and she did."

At the first sign of distress from the leaders, Cassidy made his move on Sea Siren ($5.50) and the mare sprinted clear, hanging on to beat Mental ($14) by a neck.

We're Gonna Rock ($10) came from last to take third place a further 2-1/4 lengths away.

O'Shea played down his effort in training Sea Siren to win three Group One races in her past four starts, preferring to praise the mare and her rider.

"That was just a great Jimmy Cassidy ride," O'Shea said.

"I just got her fit gradually and had her right tonight."

Sea Siren will now be aimed at the Group One Patinack Farm Classic (1200m) at Flemington on November 10, as will the slightly disappointing Buffering who weakened to finish sixth.

O'Shea will then consider a trip to the rich Hong Kong International meeting in December.

"I'd love to run her down the straight at Flemington," he said.

"I'd also love to take her to Hong Kong, it's the pinnacle of international racing in the world and I think she'd be very effective."

Buffering dropped out to finish an "inexplicable" sixth, but will press on the Patinack Farm Classic.

"He was extremely disappointing and I don't know why," said trainer Robert Heathcote.

"He had no rhythm. It was an uncharacteristically below-par performance."