One-time Blue Diamond fancy Crack A Roadie could make a late winter carnival appearance having undergone successful surgery to remove an undescended testicle.

The Stephen Theodore-trained two-year-old was found to be a rig after his autumn failure in Melbourne's premier juvenile race.

After a win and a close second at his first two starts in the spring, Crack A Roadie was aimed at some lofty autumn targets.

But things went pear shaped when he was scratched on the morning of the Inglis Premier at Mornington after getting cast in his box, and then finished last in the Group One Blue Diamond Stakes in his only run of the campaign.

Theodore described Blue Diamond day as "the lowest day" in his training career but said it was discovered that Crack A Roadie was a rig.

He has since had double surgery and will now race as a gelding.

"He was a rig. He had a testicle stuck in his intestine," Theodore said.

"It was a hot day, a pressure day on Blue Diamond day and it exposed him something horrible."

Theodore said Crack A Roadie had been given a clean bill of health after his surgery and would return to the trainer's stable from the paddock in a few weeks.

"The vets have given him a clean bill of health and they tell me horses improve six lengths after that," the trainer said.

"I know how good he is on his day, so tack on another six lengths and it's going to be very exciting for the future."

Crack A Roadie will spend another three or four weeks in the paddock before Theodore assesses what to do.

"We might have him ready for the tail end of Brisbane, but we'll just let him tell me," he said.