John O'Shea has trained many Group One winners, both as a public trainer and now as the Australian trainer for Sheikh Mohammed's powerful Godolphin operation.

But he believes Astern is top of the tree.

"I think he's the best I've trained," O'Shea said.

O'Shea's current team includes Melbourne Cup favourite Hartnell who finished second to champion Winx in last Saturday's Cox Plate, while his former stars include multiple Group One winners Private Steer and Racing To Win.

Golden Rose winner Astern gets another chance to show why his trainer holds him in such high regard in Saturday's Group One Coolmore Stud Stakes (1200m) at Flemington.

The race pits a host of quality sprinting colts against each other.

Astern's preparation has included a jump-out up the straight at Flemington last Friday in which he finished just behind Coolmore rivals Extreme Choice and Russian Revolution.

"He's ready," O'Shea said.

The colt's jockey James McDonald also has a big opinion of Astern.

"I get goosebumps talking about him," McDonald said.

"He's in good form. He's trialled up the straight so he should have got good experience from that.

"We're taking on a very good line-up of three-year-olds and he's going to have to be very good to beat them, but I think he's a very good horse."

McDonald put his faith in Astern early this campaign, choosing to stick with him heading to the Group One Golden Rose and the colt didn't let him down, powering home to win the 1400m Group One race.

Astern ran slick sectional times from back in the field last start only to be narrowly beaten by Russian Revolution in the Roman Consul Stakes.

"He developed really well from his two-year-old to three-year-old season and his two-year-old season was brilliant. So it was a scary thing to witness," McDonald said.

"He was a feisty two-year-old but he's just a man now. He's going to be taking on some exceptional sprinters but I think he's up to it."

Blue Diamond Stakes and Moir Stakes winner Extreme Choice is the $3.20 favourite in the field of 10 ahead of Astern at $3.80.

The field also features Golden Slipper winner Capitalist, Schillaci Stakes winner Star Turn and Blue Sapphire Stakes winner Flying Artie.

Astern's stablemate Archives, winner of a Group Three race last Saturday at Moonee Valley, has also earned his crack at the Coolmore having finished second in the Danehill Stakes up the straight this spring.

"He's a very good straight horse but he just might lack the class of the others, that's all," O'Shea said.