Glyn Schofield has had to surrender the ride on Doncaster Mile favourite Kementari because he cannot make the colt's weight, but he is still hopeful of picking up a Group One win at Randwick with Astoria.

Schofield had no option but to hop off the gun Godolphin colt after he was allocated 51.5kg for Saturday's $3 million feature and Brenton Avdulla takes the reins.

"I'd have loved to have ridden him but my minimum is 54 really, I'm riding 53.5kg on Saturday,"

Schofield still has a ride in the Doncaster Mile on the Chris Waller-trained Endless Drama and also rides Godolphin's Encryption in the Group One Sires' Produce Stakes (1400m).

He is most enthusiastic about Astoria's capacity to finally turn the tables on favourite Ace High in the Group One $2 million Australian Derby (2400m).

Ace High has won three races in which Astoria has run but Schofield thinks he can reverse that trend providing he can get him to settle when he backs up from last Saturday's narrow second to Levendi in the Group Two Tulloch Stakes (2000m).

"He's not going to be as keen as he was the other day and if he can drop his head and relax that'll allow him to really run the trip through," he said.

Schofield has also ridden Astoria once in last year's Group One Spring Champion Stakes in which he was fifth, four lengths behind Ace High.

The margin was trimmed to 2-1/4 lengths in the Victoria Derby (2500m), giving Schofield hope.

"Two lengths over this trip is not difficult to turn over and he's had an opportunity to strengthen up in the time in between," he said.

"He's just got to switch off and relax."

Schofield is unconcerned about the seven-day turnaround as Astoria attempts to emulate Jon Snow, who won last year's Australian Derby via the Tulloch Stakes.

"I'd like to give him an energy saving run where he's in a good rhythm," he said.

"I'll let him follow them around for the first half of the race and then work it out from there."