Ken Keys is realistic about outsider Like A Carousel's Sydney Cup hopes but has at least given his stayer every chance to produce his best in the $1.6 million race.

Like A Carousel is the $101 outsider for Saturday's Sydney Cup which has attracted class stayers headed by The BMW winner Hartnell, last year's Melbourne Cup winner Protectionist and Melbourne Cup placegetter Who Shot Thebarman.

Unlike a year ago when Keys took Like A Carousel to Randwick for the Cup only to finish among the tailenders and more than 20 lengths from the winner, the Cranbourne trainer has targeted the 3200m race this time.

"But in a nutshell we didn't expect it (the field) to be this hard," Keys said.

"That's the reality, but he's been set to be at his best tomorrow."

Like A Carousel was fourth in last year's Adelaide Cup before continuing to Sydney for what Keys said was an afterthought, with the Sydney Cup his seventh start of the campaign.

This time he heads in with fresher legs at his third start after unplaced runs in the Mornington Cup Prelude (2000m) and Mornington Cup (2400m).

"We tried to do everything last year, which was unfair to the horse, so at least he's had a proper crack this year," the trainer said.

"If he could have a top five finish we'd be very happy."

The Sydney Cup had a prize money boost this year after being a $1 million race in 2014.

So while surprised at the quality of the opposition, Keys can also see why Listed winner Like A Carousel faces a daunting task.

"I suppose when you put 1.6 million dollars up you are going to get a good field," he said.

"Previous history says it's never been this strong."

The Darren Weir-trained Akzar has been scratched from a race at Flemington and will run in the Sydney Cup.

Godolphin's Hartnell is the $2 favourite and drops 5.5kg from his weight-for-age BMW win to the limit of 52kg.

Hartnell has won over 3219m in the Listed Queen's Vase at Royal Ascot last year and trainer John O'Shea can't fault the import.

"He's probably even a little bit better than what he was in the BMW," O'Shea told RSN radio.

"He's just made tremendous improvement. He's getting up to probably his favourite trip and his favourite conditions.

"He's got a beautiful weight."