Gauging Winx's fitness is difficult for Chris Waller but the experienced trainer believes she's exactly where she needs to be to extend her winning streak to 18.

The champion completed her final piece of work at Rosehill on Thursday morning, two days out from her bid to win the Group Two Warwick Stakes at Randwick and extend one of Australasian racing's longest winning streaks.

Waller says the six-year-old mare, who won a barrier trial last week for the first time in her career, was slightly stronger than previous years.

He estimates she's seven or eight kilograms heavier than last year and up to 18kg heavier than her first Cox Plate preparation in 2015.

"It's really hard to tell with a horse like Winx, where she's at," Waller said.

"She's just so different and not knowing what to expect or how good she is, she just does things that you don't really see happening.

"Saturday is a good pointer for all of us."

But the tune-up on Thursday had Waller content his team had placed her in a great position ahead of her campaign.

"She's exactly where we want her to be," he said.

Race jockey Hugh Bowman says while the mare is usually relaxed until the business end of campaigns, she is already showing signs of nervous energy and enthusiasm for racing.

"It's interesting that she's more on the ball at this stage of the prep and there's plenty of nervous energy," Bowman said.

"It's exciting to have her so bubbly at this stage."

Winx is $1.05 for the Warwick Stakes on Saturday when a win would draw her level with 1930s marvel Ajax on 18 straight wins.

Only Black Caviar, Desert Gold and Gloaming have longer winning streaks involving at least one metropolitan race.

Winx remains odds-on favourite to win a record-equalling third consecutive Cox Plate in October.

LONGEST WINNING STREAKS IN AUSTRALASIAN RACING

(with at least one metropolitan win)

25 - Black Caviar - foaled 2006 - retired unbeaten

19 - Gloaming - 1915 - streak broken when ran second in Auckland

19 - Desert Gold - 1912 - lost in race against Gloaming

18 - Ajax - 1934 - beaten in three-horse race at odds of $1.025

17 - Mainbrace - 1947 - injury-forced retirement

17 - Winx - 2012 - unbroken - began Sunshine Coast Guineas May 2015