Tommy Berry's winning return to Sydney racing was put on hold when he lost the season's first race at Rosehill on protest aboard the wayward Liberation, giving Press Report a maiden win.

Apprentice Winona Costin, who like Berry is a Gai Waterhouse stable rider, went up against the senior jockey after the Lee Curtis-trained Press Report was taken off her line and beaten a half head in the 3YO Plate (1300m).

Berry and stable foreman Mark Newnham argued Liberation, the $1.70 favourite, was sufficiently clear when he shied at the 100m and veered left but stewards agreed with Costin the move had cost the filly more than the margin.

"It was my first protest," Costin said. "Usually I am going to Tommy and Mark for advice on things like that but I couldn't today."

Chief steward Ray Murrihy said it was clear Liberation had cost himself the race.

"We stress it is not for the panel to decide which is the best horse in the race," he said.

"It is whether the actions cost Press Report the margin and we say it does."

Curtis was thrilled Press Report ($4.60) had finally produced the win she had promised, particularly after her second to Mossfun in the Silver Slipper before that filly went on to win the Golden Slipper.

"We were originally going to race next week in the Rosebud but it was so well weighted in this race," he said.

"She got ten kilos from Liberation and she would have been badly weighted in the Rosebud because of her Silver Slipper placing.

"She will go to the Silver Shadow in three weeks and then the Golden Rose is the aim."

Because of the protest hearing, Berry missed riding Melbourne Cup favourite The Offer in a gallop between races.

The Offer edged out his Waterhouse stablemate Carlton House, running 34.63 seconds for his final 600 metres.