Given the option of two horses trained by his father Neville, Steven Parnham plumped for WA Guineas (1600m) champion, Zipaway ahead of Railway Stakes (1600m) hero, Bustler.

Parnham agonised over his decision, but said the successful record of three-year-olds in the Northerly Stakes and Zipaway's low weight of 52kg helped swayed his decision.

Parnham committed to a formula that's proved highly successful for him in the past, having ridden four Northerly Stakes winners of which three were three-year-olds.

Parnham said it was a difficult call to jump off Railway Stakes winner, Bustler, but he's confident Zipaway will be more than competitive as he rises to elite company.

"Both horses were so good to me two weeks ago," Parnham said to The Races WA.

"I never thought I'd be getting off a Railway Stakes winner at their next start.

"I've always had good luck with the three-year-olds in the Northerly Stakes.

"So, I went with the formula that has worked for me and hopefully I'm right.

"The weight differential is definitely a reason as well.

"The advantage they get against the older horses is pretty strong, the record shows that.

"I think my horse is also looking at the 1800m the way he's racing, he's always strong at the end."

Parnham said Zipway had improved since his defeat of A Lot Of Good Men and Super Smink in the G2 WA Guineas, but he'll need to up against a G1 lineup headed by Zaaki.

The nine-year-old veteran, a four-time G1 champion, has adapted well to Perth conditions and will have no excuses on Saturday, according to trainer, Annabel Neasham.

Making her Western Australian Pinnacles debut, Neesham says a month between runs and back to 1800m will help Zaaki, who will be ridden by star hoop, James McDonald.

Parnham said Zaaki is the clear threat to Zipaway in the Northerly Stakes.

"We are up against a world class horse, who has won over $10 million," Parnham said.

"He's going to be a tough ask if he is anywhere near his best.

"We will all have to be on top of our game.

"But Zipaway is in fine order and came through his run the other day.

"He's probably improved a little bit, so it's all good signs."

Parnham's brothers, Brad and Chris will partner Bustler and A Lot Of Good Men respectively.

Three years ago Chris joined his brother Steven on the Northerly Stakes honour roll after combining with Truly Great for Grant and Alana Williams.

Steve currently shares the Northerly Stakes riding record with Paul Harvey following wins on Playing God (2011-12), Ihtsahymn (2014) and Kay Cee (2020).

Ahead of tonight's (Tuesday) barrier draw, Zaaki is favourite at $2.45.

Alsephina and Zipaway are $8.50. A Lot Of Good Men is $11.