Celestial Legend gave the three-year-olds bragging rights over the older horses in the Doncaster Mile, now a trio from that age group will be out to repeat the dose in the Group 1 All Aged Stakes.

Australian Guineas winner Southport Tycoon, Hobartville Stakes runner-up Encap and filly Tiz Invincible form the three-year-old contingent in Saturday's 1400 metre showpiece.

Nine have won the race in the past 40 years, four of them in the past decade including Giga Kick 12 months ago.

But having partnered Celestial Legend to his breathtaking Doncaster Mile success under handicap conditions, jockey Tyler Schiller knows the task Encap faces when he links with the gelding at Randwick on Saturday.

"It's a big assignment up to the Group One, weight-for-age, but he's a chance," Schiller said.

"He just has to get the first half of his race right."

Schiller has partnered Encap once before, the Gary Portelli-trained gelding storming home to finish second in a Warwick Farm maiden in August.

Two starts later, he captured the Group 3 Ming Dynasty Quality (1400m) at Rosehill before beating all but Militarize in the Group 1 Golden Rose (1400m).

Encap kicked off his campaign with a brace of stakes placings and was a luckless fifth behind Celestial Legend in the Randwick Guineas (1600m) when badly held up for a run.

While he wasn't disgraced against the older horses in the George Ryder Stakes (1400m) at his latest appearance, settling in the second half of the field and doing his best work late to finish sixth, Schiller wants to see him position himself more prominently on Saturday.

"Gary said he's kept him fresh, so hopefully he can get that start right and if he can put himself fifth or sixth, he's got the turn of foot to put himself in the finish," Schiller said.

Pre-post markets indicate the mares hold the key to Saturday's race with Espiona a $3.90 favourite ahead of Sunshine In Paris ($4.80).

Southport Tycoon, shooting to become the first colt since Flying Spur in 1996 to capture the Australian Guineas-All Aged Stakes double, is rated the pick of the three-year-olds at $6, with Encap a $15 chance.