Ciaron Maher’s promising colt Observer, the unlucky runner from the Caulfield Guineas, is set to run at Moonee Valley on Saturday — but which race he contests remains undecided.

The Group 2 Drummond Golf Vase appears the likely option as a stepping stone toward the Victoria Derby (2500m), though connections have also floated the possibility of a shock start in the Cox Plate.

A $200,000 late entry fee would be required for the colt to line up in the Cox Plate, with the final field to be confirmed on Tuesday.

Maher’s assistant trainer Jack Turnbull said the decision rests with Godolphin’s Andy Makiv, Jason Walsh and Maher.

“We are more than likely Vase, but whether that changes is up to Andy, Jason and Ciaron,” Turnbull said.

Observer finished a luckless third behind Autumn Boy in the Caulfield Guineas, and Turnbull believes the colt still has more to give.

“The Group 1 placing was great, but there’s still plenty left there,” he said.