Vahala had genuine concerns about Aztec Ruler before The Joey and despite the four-year-old finishing a credible sixth behind Magnificent Andy his fears were unfortunately borne out.

With Steven Parnham aboard, Aztec Ruler presented strongly in the straight, but coming back from a minor injury setback, six weeks between races and a wide run throughout proved too high a hurdle to overcome in The Joey.

"He pulled up super and just ran out of fitness on us," Vahala said to The Races WA.

"It looked like he was going to win there for a bit, but run out of gas.

"Six weeks between runs, tough run and missed a bit of work as well.

"It was just a combination of everything, but anyway, that's what happens."

Vahala has no doubt Aztec Ruler is back on top of his game and fully fit after foot bruising kept him out of the Grandstand Cup (1500m), won by Northam Stakes rival, Mood Swings.

It came as a mini blow for Vahala and the timing astray with Aztec Ruler on song after coming out of a career-best win in the Listed Bunbury Stakes (1400m) in March.

"He's awesome and the one benefit off that tough run is we have our fitness back," Vahala said.

"He hasn't missed a beat and is bouncing out of his skin, so I'm pretty excited to see what he can do .

"This is probably the best field he's ever been against and it will be pretty awesome to see where he's at.

"He's going really good, galloping really well, feeling really well, we will get to see him at his best."

In a quality field of 14 starters, Aztec Ruler will jump from barrier 12.

After racing handier in the Bunbury Stakes and The Joey, Vahala expects jockey Steven Parnham to take a more conservative approach.

"I'm hoping Northam will play a little fairer than Ascot," Vahala said.

"I would like to think we can use that turn of foot a bit more and go back a little bit.

"Like every race I leave it up to Steve, but I probably will tell him to be a bit more conservative than aggressive."