John Sadler is hoping a fitness edge and a growing affinity with the Flemington straight track will shine through for Lonrockstar.

The son of Lonhro lines-up in the Group Three Aurie's Star Handicap (1200m) on Saturday, his fourth straight race at the Flemington course in as many starts.

Lonrockstar is taking on resuming dual Group One-winner Trust In A Gust in Saturday's race and Sadler is banking on race fitness giving his sprinter an edge.

"The horse is good, he's had a freshen and he's got a bit of an affinity with the straight," Sadler said.

"Being this time of the year I think it's not a bad race for him.

"He's got that fitness racing through the winter and at this later part of the winter you've got an edge on some of those better horses.

"But it can change around towards the end of the month when those horses get fitter."

Sadler said the six-year-old was decidedly unlucky at his first attempt on the straight course when badly held-up for a run, before winning over 1100m on June 27.

At his last run he finished second in the All Victorian Sprint Final behind Play Master on July 11.

Sadler said he has no ambitious plans with Lonrockstar who will be ridden by Glen Boss on Saturday.

The trainer also saddles Charmed Harmony while a decision is pending on stablemate Henwood also contesting the Louis Polgar & Jason Vance Handicap (1400m).

He said Henwood may be reserved for a race at Sandown next Wednesday.

Sadler's son Tom replaces the injured Katelyn Mallyon aboard Charmed Harmony after the in-form apprentice guided him to victories at Caulfield and Flemington over 1400m at his last two starts.

Most Wanted finally makes his debut in the Elizabeth Dunkley & Jason Lee Handicap (1400m) under Damien Oliver after a sale to Hong Kong fell through.

The gelding was scratched from engagements at Flemington on July 18 and Caulfield on July 25 pending the sale being finalised.

"I'm not all that sorry about it because I think he has the makings of being a reasonable horse and we'll get an idea of that on Saturday," Sadler said.