The second-highest-rated horse in Australia, Hartnell, is the odds-on favourite to bounce back and win the Ranvet Stakes at Rosehill after a disappointing showing at his most recent start.
With champion Winx running in today's George Ryder Stakes (1500m) on the same programme as the weight-for-age Ranvet (2000m), it gives Hartnell a golden opportunity to land a third career group one win and keep an unbeaten record at Rosehill intact.
The Ranvet is the first of five group one races on the Golden Slipper programme and victory to Hartnell ($1.90) would give visiting jockey William Buick his first Australian group one success.
The Godolphin hoop also rides Hauraki and Trekking in group one races today.
Hartnell goes in off a last-start eighth in the Chipping Norton Stakes at Randwick on heavy going, the only time this season the gelding has not finished among the placings.
He has not raced at Rosehill since March 2015, when he won the Sky High Stakes (2000m) and the BMW (2400m) in consecutive starts.
"There were genuine excuses for him last start, but again, he's going to find a track on Saturday that is wet," trainer John O'Shea said.
"He looks to be back to his best and he would need to be near his best to be in the finish of this race.
"We just need to get him back in the game and get a good positive run leading into the Queen Elizabeth and hopefully he does that on Saturday.
"We're very happy with him. He's in great order and I'm sure he'll bounce back."
It was only 12 days between Hartnell's first-up second to Winx in the Apollo Stakes and his unplaced Chipping Norton run and O'Shea is happier with a more suitable spacing this time.
"Three weeks has always been his ideal time between runs," the Godolphin trainer said.
"He takes a week to get over his run and then he gets into his groove and he starts throwing his head around. He's done that this week so we're looking forward to Saturday."
Last year's winner, The United States, is on the second line of betting at $5 with Antonio Giuseppe and Stratum Star both at $9.50 in the field of eight.
• Deja vu, all over again.
That's the scenario Chris Waller has prepared supermare Winx for at Rosehill, as her George Ryder Stakes rivals again contemplate the race for second place.
The world's greatest horse on turf wrapped up her trackwork for the defence of one of her multiple group one crowns in typically damp conditions in Sydney on Thursday, with intermittent showers so far water off a duck's back for Waller and jockey Hugh Bowman. Winx breezed over a heavy 9 at Randwick for her second Chipping Norton Stakes victory on February 25, and three weeks later the 5-year-old is odds-on to handle similar conditions on home ground.
"She's feeling stronger than ever," Bowman said.
Waller was also upbeat about Winx racking up her 16th straight win on Golden Slipper Day when she faces eight rivals in the A$1 million weight-for-age feature over 1500m.
"It was great to hear Hugh's comments after he dismounted saying 'she's as good as we can get her'," he said. "Her condition is exactly where we want it to be."
Winx was at $1.15 with the TAB on Thursday with star sprinter Chautauqua at $8 as he attempts the distance for the first time.
Le Romain, who beat Chautauqua in the group one Canterbury Stakes at Randwick on March 4, was at $11.