Tommy Berry's Doncaster Mile booking for First Seal will also come with a change of riding tactics for the Group One-winning mare.

Trainer John Thompson said it was likely First Seal would be ridden off the speed in the $3 million race at Randwick on Saturday week.

A first-up winner against fillies and mares, First Seal has raced close to the front at her past two starts at weight-for-age for a Canterbury Stakes placing and a fourth-placed finish behind Winx in the George Ryder Stakes.

First Seal will drop from 57kg to 53kg in the Doncaster.

"A bigger field in a race like the Doncaster will suit her because she can sit back and let the others do the work up front," Thompson said.

Berry takes over from Blake Shinn because the Golden Slipper-winning jockey can't ride at 53kg.

Melbourne jockey Glen Boss has taken the Doncaster ride on lightweight Azkadellia.

Runner-up in the Coolmore Classic at her first Sydney start, Azkadellia has 50kg.