Co-trainer Simon Zahra is convinced Heatherly will strip a fitter mare in the McEwen Stakes as she continues on a path to the Group One Moir Stakes.

Heatherly was chased down by another quality mare, Missrock, in the Listed Carlyon Stakes at Moonee Valley first-up two weeks ago and that pair form part of a small-but select seven-horse field for Saturday's Group Two McEwen (1000m) at the same track.

Heatherly's connections considered whether to go straight to the $500,00 Moir Stakes (1000m) on September 29 but decided to include the McEwen in her program rather than go five weeks between runs.

"She has come on a bit from her first-up run," Zahra said.

"Those better horses take a while to get fit because they do everything pretty easily on the track.

"She actually had a really good blow after the race the other day and she seems a lot better now. Her coat is nearly there so she'll improve again and then hopefully be set for the Moir."

Three-year-old filly Houtzen is the $2.60 favourite ahead of Group One winner Russian Revolution ($3.50) and Heatherly ($6).

Houtzen is taking on the older horses for the first time and has 50kg under the weight-for-age conditions, between 6.5kg and 8.5kg less than her rivals.

"Obviously it's a better quality field than the other day and there looks to be plenty of pressure in the race," Zahra, who trains in partnership with Mathew Ellerton, said.

Zahra expects Houtzen to put pressure into the race, with Russian Revolution another on-speed runner while Heatherly is also known as a free-rolling sprinter but can also take a sit.

"We'll just leave it up to Damian Lane, and how she jumps will have a bearing as well on where she ends up," Zahra said.

"It will be an interesting race."

The upcoming Moir Stakes could be a career-defining race for Heatherly.

"We'll just evaluate from there whether she retires and goes to stud or we go on," Zahra said.

"That will be the crossroads."