Trainer Henry Dwyer will have a foot in both camps after booking premiership-chasing jockeys Craig Williams and Beau Mertens for rides in separate races at Caulfield.

Williams leads apprentice Mertens by one win in the Melbourne title race and Saturday's Caulfield program is the first of nine city meetings in the final month of the season.

Dwyer has three Caulfield runners and has booked Williams for Act Of Valour in the Ladbrokes Handicap (1200m) while Mertens rides If Not Now When in the Sheamus Mills Bloodstock Handicap (1100m).

"It's just by design that you try to get the riders in form on your horses," Dwyer said.

"Beau is riding well and Craig is riding well, so I'm happy to have them on."

Three-year-old If Not Now When is a $15,000 yearling who has won close to $280,000 prize money in 10 starts, the lion's share coming courtesy of wins in the restricted VOBIS Gold Rush at Bendigo and another VOBIS Gold race at Cranbourne in her first two starts more than a year ago.

She hasn't won since but has been competitive in her past three city races and returns to her home track on Saturday having run second to stablemate Snitty Kitty three starts ago with a light weight.

"She's racing as well as she can and she needs circumstances to go right," Dwyer said.

"She doesn't really go inside horses because I think she gets a bit intimidated being a small filly.

"So she needs to settle midfield or worse on the outside and be on a track where they can run on."

Dwyer says If Not Now When doesn't cope with big weights and her handicap rating has not gone down despite her not winning for a year.

But he is hopeful the 56.5kg after Mertens' claim is a winnable weight.

Act Of Valour won in Adelaide two starts ago before finishing second in another $100,000 Morphettville race in May.

He was due to contest last month's Echuca Cup but hurt himself when he played up in the float.

"He was a late scratching and did a little bit of damage to himself and had to have a couple of weeks in the paddock," Dwyer said.

"But he's back and in good order. We thought we'd run him at Caulfield as we can just walk him to the races.

"He's had seven weeks since his last run but he's a horse who races better fresh anyway."