The focus might be on Chris Waller's Zoustar in Saturday's Coolmore Stud Stakes, but the trainer was monitoring the progress of his premier stable's lesser-known horses in a midweek race at Warwick Farm.

Perplexity, Instrumentalist and Bit Of A Hero filled the first three placings in the Edgar Britt 100th Birthday Handicap (2200m) on Wednesday, a race Waller said was a good test of their staying ability.

"They all went well and they will all win these types of races," he said.

Waller decided to pit the three stablemates against each other because he felt the field lacked depth at nomination time.

Waller said the winner Perplexity, a four-year-old gelding, had been "chipping away" and building up to a longer distance.

"The writing's been on the wall that he's looking for a trip, the way he likes to settle in the early part of his races," he said.

"It's still a big test to do it, and he's done a good job."

Jim Cassidy, who stuck with Perplexity after partnering him at his previous two starts, said he had no doubt the horse would run out the journey.

"He just keeps going. He's a bit of a one-batter and once you get him up there, he keeps rolling off one bat," Cassidy said.

Cassidy will team up with Waller when Zoustar attempts to win his second Group One race at Flemington.

His jockey is a little more seasoned at the top level and will be chasing his 100th Group One win aboard the odds-on favourite.