Rebel Raider is primed for victory in the South Australian Derby with his recent Sydney failures still a mystery to trainer Leon Macdonald.The Victoria Derby winner failed to show anything of the form that won him the Flemington classic in the spring and was taken home to Adelaide after three Sydney runs.Exhaustive veterinary checks in Sydney after his second last in the Rosehill Guineas failed to show any signs of injury with Macdonald believing the clockwise direction of racing may not have be

Rebel Raider is primed for victory in the South Australian Derby with his recent Sydney failures still a mystery to trainer Leon Macdonald.

The Victoria Derby winner failed to show anything of the form that won him the Flemington classic in the spring and was taken home to Adelaide after three Sydney runs.

Exhaustive veterinary checks in Sydney after his second last in the Rosehill Guineas failed to show any signs of injury with Macdonald believing the clockwise direction of racing may not have been to his liking.

Rebel Raider was back to his best in the Listed Chairman's (2000m) at Morphettville on April 18 and immediately rocketed to the top of the markets for Saturday's SA Derby (2500m).

"The only race that really disappointed me was the Rosehill Guineas," Macdonald said.

"He had every test done on him in Sydney and they couldn't find anything wrong.

"Personally I think it has to do with the bone spur he has on his off side hock.

"He has always had it and maybe it affects him going the other way around.

"Or maybe he just doesn't like going that way.

"Whatever happened, the South Australian Derby looks like a pretty good consolation."

Punters believe the biggest challenge to Rebel Raider, who is at $3.20 with TAB SPortsbet ahead of Wednesday's final acceptances, is Victorian Larry's Never Late ($4).

The Rod Douglas-trained Larry's Never Late earned his place in the Derby with victory against older horses in the Hamilton Cup (2200m) on April 19.

The gelding is by noted sire of stayers Pentire out of Laebeel, a close second to Sky Heights in the 1999 Caulfield Cup with third placed Inaflury completing an historic trifecta for champion stallion Zabeel.

"He has the breeding and has earned his chance in the Derby," Douglas said after the Hamilton Cup win.

Larry's Never Late ran sixth in Rebel Raider's Victoria Derby and Macdonald agreed he was the one to beat on Saturday.

Sydneysider Naval Escort travelled to Adelaide last week with champion sprinter Takeover Target with trainer David Payne to oversee the final leadup on Tuesday.

Naval Escort ($9) came from last on the turn to finish sixth in the AJC Australian Derby won by Roman Emperor after being held up for a run.

"I think he could have finished a bit closer in the Derby if he had got clear," Payne said.

"He is by Montjeu so he is bred to stay.

"All the reports are that he has settled in well in Adelaide and I think he can perform well."