Adelaide trainer Gordon Richards is convinced his stable star Gytrash has improved since his Lightning Stakes win as he prepares to chase a big sprint double at Flemington.

Gytrash upstaged Redzel, Loving Gaby and Nature Strip to win the weight-for-age Group One Lightning (1000m) on the straight track at Flemington last month when first-up from a spell and he is unbeaten from three attempts at the course.

Saturday's Group One Newmarket Handicap (1200m) at Flemington has been a long-range target for the four-year-old since his spring campaign last year was cut short, and Richards is confident he will be hard to beat.

Gytrash is set to carry top weight of 57kg, with handicaps to be raised 1kg at acceptance time on Wednesday after Nature Strip's defection from the race.

"When we had to abort the spring the Newmarket was a logical target for him with his affinity for racing at Flemington," Richards said.

"The lead-up was probably always going to be the Lightning and to win it was probably a bonus even though I thought he was a really good chance in it."

In the immediate aftermath of Gytrash's one-length Lightning win on February 15, Richards said there was still improvement to come.

Nothing has changed that opinion.

"I believed that at the time because he had only had a couple of gallops leading into the Lightning," Richards said.

"At the last minute I thought I had him a little underdone, only on the amount of gallops he'd had leading up to it. He was always going to be better after, so I believe he has improved.

"It's good for us. Whether it frightens the others off, I don't know. But I'm pretty upbeat about him on what he's done since.

"He hasn't gone backwards at all. I'm pretty happy with him."

Gytrash was at $7 on Tuesday behind a trio of Group One-winning three-year-olds - colts Bivouac and Exceedance and filly Loving Gaby - all at $5.

Mark Zahra will be in Sydney to ride Super Seth and Santa Ana Lane in feature races at Randwick on Saturday, meaning Ben Melham has been given the chance on Gytrash.

"He's a big-race rider and I'm happy for him to be riding him," Richards said.