Expat Australian Ian Wilkes has already trained a Breeders' Cup Classic winner and will have his first runner in the most famous American race of all when McCraken lines up in the Kentucky Derby.

McCraken is the 5-1 joint second favourite for the Run To The Roses at Churchill Downs on Saturday (Sunday AEST).

Although McCraken is Wilkes' first Derby starter, it is far from his first experience with the race. He was the exercise rider for 1990 winner Unbridled and assistant to trainer Carl Nafzger with 2007 winner Street Sense.

Although McCraken missed the Tampa Bay Derby on March 11, Wilkes said it was not a problem.

"I felt confident we would be OK. It was very minor," Wilkes told Churchilldowns.com.

"Things happen for a reason, so we will find out in the long run."

Nafzger was a spectator on Thursday morning when McCraken galloped over 1800 metres.

"I'm so proud of him," Nafzger said of Wilkes. "It is like watching your son score the winning touchdown in the big game for the home team.

"Ian was a big influence with Unbridled and Street Sense. We always bounced stuff off each other. We always worked together."

Wilkes, whose brother Wayne is a trainer in country NSW, worked for trainers Paul Sutherland, Vic Thompson and Colin Hayes in the 1980s before moving to Kentucky to become Nafzger's work rider in 1989.

He then returned home for three years before he was lured back to Louisville in Kentucky to become Nafzger's assistant.

He took over most of Nafzger's horses when the trainer went into semi-retirement in 2006 and in 2012 trained Fort Larned to win the Breeders' Cup Classic.