Peter Robl will team with in-form trainer Gai Waterhouse in search of a Winter Cup victory aboard Reuben Percival at Warwick Farm.

Peter Robl links with the in-form Gai Waterhouse stable, upbeat about his prospects of a feature race victory on Reuben Percival in Saturday's Winter Cup at Warwick Farm.

Reuben Percival forms part of a strong book of eight rides for Robl which includes talented juveniles Ninth Legion and Diamond Earth for Anthony Cummings.

Reuben Percival was a convincing winner at Hawkesbury two starts ago before his third in the Listed McKell Cup (2400m) on May 20.

The gelding was installed equal $4.60 favourite for Saturday's 2400m event with TAB Sportsbet on Wednesday alongside McKell Cup winner Adroitly in a field of 12.

"His win at Hawkesbury was terrific and he was very brave at Randwick last start on the wet track," Robl said.

"I would imagine it would more than likely be rain affected again on Saturday and the way he's going gives him a terrific chance, especially with 54 kilos on his back."

Robl rides work one day a week for Waterhouse and while he's never ridden Reuben Percival in a race, he doesn't see it as an issue.

He wore the same colours to victory in the 2010 Group Two Hill Stakes aboard Descarado.

"I've seen his racing pattern and watched him race plenty of times and have got a pretty good handle on how to ride him," he said.

Robl and Cummings, meanwhile, have enjoyed a good run of late with the stable's up-and-coming horses and the jockey believes it can continue at Warwick Farm.

Ninth Legion, who'll line up in the Regupol Equine Safety Surfaces Handicap (1400m) scored at Canterbury on debut and is one of 16 juveniles still entered for Saturday week's Group One TJ Smith (1600m) in Brisbane.

"It wouldn't surprise me if he came out and won convincingly (on Saturday)," Robl said.

"He's got all the attributes of a nice horse.

"Naturally he's going to be better as a three-year-old, he's got plenty of upside and I think in time he can definitely measure up to the better races."

Diamond Earth has won three races this season, including a last-start success over 1100m at Scone, and strikes another suitable assignment in the Ambassador Travel Services Plate (1100m).

"What a great ride it's been on her since I've been back riding," Robl said.

"She's a deadset pocket rocket."

After the filly's Scone win, Robl believes the 1100m suits the speedster even better than 1000m races.

"It looks a perfect race for her and she'll give them something to chase," he said.