New Zealand trainer Roger James has expressed surprise at the weight top mare Silent Achiever has to carry in the Melbourne Cup.

Silent Achiever, who has her next start in Saturday's Group One Underwood Stakes, has 56.5kg in the Flemington 3200-metre race.

Makybe Diva, when successful in her third successive Cup in 2005, is the only mare to have won with more weight when carrying 58kg.

"She's weighted right up there," James said.

"I haven't had a chance to look at history but I would think there wouldn't be too many mares in recent years anyway that have been asked to carry that sort of weight."

James has been keen to get the mare to the Melbourne Cup but didn't rule out shifting the focus to the weight-for-age Cox Plate.

"Look, today's weight release might well change our focus a bit," he said.

"I'm not saying we will, but we could.

"I haven't had the time to look at statistics or discuss it with the owner.

"But I was a tad surprised."

Racing Victoria's chief handicapper Greg Carpenter released the Melbourne Cup weights on Tuesday with Japanese galloper Admire Rakti topweight with 58kg.

Carpenter said the rules dictated that there must be a minimum topweight of 58kg and with no "natural topweight" in the nominations this year, it bumped up a majority of horse's weights by 2kg.

That is why Silent Achiever has 56.5kg in the Melbourne Cup and was originally weighted on 54.5kg in the Caulfield Cup.

James has said he will wait until after the Turnbull Stakes before deciding whether Silent Achiever's preparation would take in the Caulfield Cup or Cox Plate, and said there were positives and negatives with both options.