If one jockey's misfortune can create an opening for another rider, Adam Hyeronimus is well placed to make the most of his only chance at Rosehill.

At the expense of sidelined stable jockey Tommy Berry, Hyeronimus has been rewarded for his work ethic with the ride on richly-bred filly Mardi for trainer Gai Waterhouse on Saturday.

Since coming out of an apprenticeship interrupted because of a long suspension, Hyeronimus has applied himself to the point where he is well entrenched in a demanding but often rewarding culture that the day-to-day workings of Tulloch Lodge can provide.

"I finished the last 12 months of my apprenticeship with Gai and I have stayed there ever since," Hyeronimus said.

"Gai has been fantastic to me as a person as well as a horse trainer who has guided me through the racing industry."

In recent months, Hyeronimus has graduated from riding Waterhouse's provincial team on Saturdays to filling a void when Sydney's best jockeys migrated to Melbourne for the spring carnival.

It's a move he would like make full-time but the 23-year-old is happy for his boss to make the call.

"Pretty much where Gai wants me to ride I will ride but I feel I've been riding good enough and having enough luck to stay in town so hopefully it can snowball a bit from there," he said.

Waterhouse is on a European holiday but her absence this time hasn't affected the closely scrutinised Tulloch Lodge strike-rate.

Hyeronimus contributed to the stable's streak when he rode two of its three winners at Wyong on Thursday.

"Gai's horses are flying at the moment and obviously I'm there most mornings riding trackwork, putting in the hard work," Hyeronimus said.

"It's a great team environment to be around."

Redoute's Choice filly Mardi is challenging for favouritism in the TAB Rewards Handicap (1400m) after winning first-up for Berry at Canterbury.

"She's a very well-bred filly and in her first start she had to do a lot of work in her win," Hyeronimus said.

"And the fact she is out of Bianca, who won a Wyong Cup, means she's only going to get better as the races get further."