Hallowed Crown has had the measure of Sweynesse in two autumn races but the Rosehill Guineas presents a new challenge for the rivals.

Hallowed Crown steps to 2000m for the first time in search of a third Group One win while Sweynesse has already been to the trip twice and it's a distance Godolphin trainer John O'Shea believes can be the colt's best.

"I always thought that was his optimum distance," O'Shea said.

Sweynesse has performed admirably in the Hobartville Stakes (1400m) and Randwick Guineas (1600m) but it has been Hallowed Crown which has taken most of the plaudits.

They are joint favourites in the opening Guineas market in a field which includes New Zealand Derby winner Mongolian Khan and runner-up Volkstok'n'barrell.

The race looms as potentially Sweynesse's best chance this campaign to land a decision over Hallowed Crown and notch a breakthrough Group One win.

"He hasn't been ready yet (this campaign). He's getting close to being ready Saturday," O'Shea said.

While Sweynesse has been narrowly beaten, his owner Sheikh Mohammed has still come out a winner in the Hobartville and the Randwick Guineas as the part-owner of Hallowed Crown who will eventually stand at Darley Stud.

Sheikh Mohammed bought into Hallowed Crown after his Golden Rose last year, but the colt continues to race in the colours Gooree Stud.

"He's a horse that we identified as being a horse that we wanted Sheikh Mohammed to have an interest in. So to quinella those two lead-ups was a big result for the company and Sheikh Mohammed and hopefully we can do it again on Saturday," Godolphin racing manager and Darley's Australian bloodstock manager Jason Walsh said.

Sweynesse raced at 2000m during spring, finishing third to Guineas rival Hampton Court in the Spring Champion Stakes before being beaten less than two lengths by the best weight-for-age horses when eighth in the Cox Plate (2040m).

Gai Waterhouse has Hampton Court backing up after he tired for sixth in the Phar Lap Stakes.

Waterhouse didn't believe the way the race was run suited the colt but expects a fitter horse to step out, noting he won the Spring Champion backing up a week after he won the Dulcify Quality.

ROSEHILL GUINEAS

* Second leg of the Sydney autumn three-year-old triple crown after the Randwick Guineas (1600m) and preceding the ATC Australian Derby (2400m)

* First run in 1910 when won by Electric Wire

* Favourites successful since 1980: Kingston Town (1980), Sky Chase (1988), Riverina Charm (1989), Surfers Paradise (1991), Octagonal (1996), Carnegie Express (2002), Niello (2004), Metal Bender (2009), Jimmy Choux (2011) and It's A Dundeel (2013)

* Nine Guineas winners since 1980 went on to win the Derby - Kingston Town (1980), Strawberry Road (1983), Naturalism (1992), Innocent King (1993), Octagonal (1996), Sky Heights (1999), Eremein (2005), It's A Dundeel (2013) and Criterion (2014).