James McDonald is losing weight but there is no sign of him losing form at one of the most important times of the year for a top jockey.

He may have his mind on riding Caulfield Cup chance Rising Romance at 53kg, but that didn't stop the star jockey from securing a winning treble at Warwick Farm on Wednesday.

McDonald said he was on target to keep a promise to New Zealand trainer Donna Logan to ride the mare at her right weight in Saturday's Caulfield Cup.

"I've got about a kilo and a bit to go to make the weight," McDonald said.

Rising Romance ran her best race of the spring when she finished second to Moriarty in the Craven Plate at Randwick, prompting McDonald to stick with the horse he rode to win this year's ATC Australian Oaks.

The most impressive of McDonald's three Warwick Farm winners was Greco, a Hawkes Racing-trained three-year-old who resumed to take out the Time To Shop At TAB Maiden Plate (1100m).

Greco started favourite at $2.20 and won by five lengths on a heavy track.

Co-trained Trainer Michael Hawkes said the gelding had come a long way.

"We've had a few issues with him, obviously in the barriers," he said. "He had to be scratched at Canterbury a while ago and we've had to work on him."

McDonald said his mount handled the wet track with a minimum of fuss.

"It is heavy, very testing, but my horse got through it well," he said.

Fresh from winning the Caulfield Guineas at the weekend, the Sydney-based New Zealander also won the Testa Rossa @ Vinery Plate on Aerobar before steering the Chris Waller-trained favourite Just A Girl to victory in the TAB Betting a Season Handicap.

The 23-year-old celebrated his first Sydney jockeys' premiership this year and is on target to go back to back with his treble taking him to the lead in the 2014-2015 title.