In his long career as steward, Racing Victoria chief Terry Bailey for the first time saw a new way for a horse to be declared a non-runner.

Seattle Park, the fourth placegetter in Wednesday's Polytrack Handicap, was denied a fair start to the 2100m race after stewards established the horse had his tail caught between the two gates at the back of the barriers.

Rider Craig Williams estimated Seattle Park missed the start four lengths before finishing fourth, three-quarters-of-a-length behind third placegetter Amerock.

Bailey told Mick Kent junior, representing his father, trainer Mick Kent, that starter Cory Mallyon had brought the incident to stewards attention before riders had weighed in.

Under the rules of racing if a horse is found to be denied a fair start and doesn't finish first, second or third it will be declared a non-runner.

After deliberating, stewards said what happened at the start had materially affected the result of the race.

Being declared a non-runner has cost connections of Seattle Park $2000 in prize money.

"We sympathise with the owners but we also have to protect the punters who have backed the horse," Bailey said.

Had Seattle Park finished in the first three placings, he would have been declared a starter.