Assertive Play's introduction to Melbourne racing will give trainer Phillip Stokes a clearer picture on whether the unbeaten Adelaide filly is a Thousand Guineas contender.

"It's a really tough year this year. I think there's a lot of good three-year-olds," Stokes said.

"We will head her that way, but if we think she maybe is not quite up to that she could always go to the Edward Manifold Stakes or something."

The Group Two Edward Manifold (1600m) for fillies at Flemington on October 6 is a week before the Group One Thousand Guineas (1600m) at Caulfield.

Stokes is yet to win a Guineas but has won two Manifolds with Maybe Discreet (2012) and Serenely Discreet (2016) and a Group Two Thousand Guineas Prelude in 2015 with Miss Gunpowder.

Assertive Play won twice at Morphettville in June before a let-up, and Stokes has opted for a gear change for her return race on Saturday at Moonee Valley, removing a near-side blinker.

"We've put a bubble cheeker on her just to try to make her go a bit straighter because she had a habit of hanging in," he said.

"She does still lay in but nothing like she was so I'm happy about that.

"In her two trials she has gone a lot straighter than in her two races so we're happy enough with the gear change and think that will help."

Assertive Play was at $11 on Thursday for Saturday's Listed Atlantic Jewel Stakes (1200m) while Stokes is waiting another week to run Music Bay.

Unbeaten Anjana and Quezette Stakes runner-up Humma Humma were equal $5 favourites.

"I think she'll be better when she gets over a bit further but I expect her to be running on," Stokes said.