An elder statesman of Sydney racing has paid Winona Costin the ultimate compliment as the Tulloch Lodge apprentice prepares to build on a city winning streak at Warwick Farm.

"She is the best female rider I have seen at this stage, and I have been in racing for 50 years," Melbourne Cup-winning trainer Les Bridge said.

Bridge's evaluation of Costin's talent came after she rode five winners in 48 hours, including one for the veteran Randwick trainer on Sunday.

Costin's star has been on the rise since she became indentured to Gai Waterhouse midway through the 2013-2014 racing season.

And Tulloch Lodge's Mark Newnham is backing her to go all the way after answering the first serious challenge of her apprenticeship.

"She's always had natural ability, but at least with her reduced claim now she's kept improving which she has to," Newnham said.

"When you go from (claiming) three kilos to two kilos you've got to ride better - and she has."

Costin has mounts in six of the seven Warwick Farm races on Wednesday, including Zindzela for Waterhouse and Magwitch for Godolphin trainer John O'Shea.

Zinzelda makes her first city appearance in the Hyland Race Colours Handicap after an on-pace Kembla Grange win.

Godolphin colt Magwitch is also in winning form and he returns to metropolitan class following Kembla Grange and Newcastle victories wins at his past two starts.

Country and provincial trainers provide the rest of Costin's book and she will ride Spanish Shoes (race two), It's A Virtue (race five), Darci's Affair (race six) and Choice Larga (race seven)for out-of-town stables.

Costin has established an impressive early lead in the race for the Sydney apprentices' title with her Rosehill win on Road To Summer on Saturday taking her tally to 17.

Her nearest rival Taylor Marshall has ridden six winners but he has only one opportunity to improve on that tally on Wednesday.