His trainers have long thought he would stretch beyond a mile and Ellsberg will get an opportunity to prove them right when he contests the inaugural staging of the $2 million Five Diamonds at Rosehill.

The entire is a Group 1 winner up to 1600m having dead-heated for first with Top Ranked in last month’s Epsom Handicap at Randwick over a circuit regarded as one of the most testing miles in Australian racing.

He will extend to 1800m on Saturday and while co-trainer Gerald Ryan concedes the extra journey is a query, he can also see no reason Ellsberg won’t run it out strongly.

“If he is ever going to run it, he’ll run it now when he’s at the peak of his game,” Ryan said

“Right from a young horse when he ran third in the Spring Stakes at his third start in a race at Newcastle, we always thought he would run at least 1800 metres.

“We never had a chance or thought of going there (after that), it’s just that this was a nice race for him, so when they announced the race in the autumn, we aimed towards it.”

Brenton Avdulla has ridden Ellsberg to his past two wins in the Epsom and Five Diamonds Prelude but will be at Flemington on Saturday for the mount on Private Eye in the Champions Mile.

In his absence, Tommy Berry has picked up the ride and got a feel of the horse in a trackwork gallop last weekend.

“He galloped on the course proper on Saturday morning, Tommy Berry rode him and he worked really well,” Ryan said.

“He backed it up again (Tuesday) morning so he will be left alone for the rest of the week now.

“The race is probably a fraction stronger than what I thought it was going to be but he’s going well.”

Ellsberg headlines a field of 13 for the Five Diamonds and has opened a $2.60 favourite, ahead of Laws Of Indices ($5) who returns to Sydney following some strong performances in Melbourne, albeit on rain-affected tracks.

One of few horses to make ground from the back when runner-up in the Toorak Handicap two starts ago, Laws of Indices then finished just over 2-1/2 lengths from Anamoe in the Cox Plate last time out.

He is one of two Five Diamonds runners for Annabel Neasham, along with Sibaaq who is set to back up from his third in the Big Dance at Randwick on Tuesday, as is the winner Rustic Steel.