Junoob's first Australian stakes win has posed a programming dilemma for trainer Chris Waller.

The former English horse made it three wins from his past four starts when he took out the Listed Randwick City Stakes (2000m) on Saturday.

After finishing third to his stablemate Opinion in the Parramatta Cup, Junoob put five lengths on his stablemate on a firmer track.

The premier trainer said Junoob was unlikely to back up in next week's Group One Ranvet Stakes and probably did not have the staying credentials for the Sydney Cup (3200m).

"The ideal race for him is the Neville Sellwood Stakes on Golden Slipper day but it's been changed to set weights with penalties which may not suit," Waller said.

"He may well be a very, very good 2000-metre horse and not a stayer.

"The Ranvet is unlikely."

Opinion will be stretched to 2400 metres for his next start in the Group Three Manion Cup in two weeks.

"Junoob improved on top of the ground while Opinion is better on a softer surface," Waller said.

"I think that was the difference today."