The fall which has left jockey Luke Nolen with serious injuries has been ruled an accident.

Nolen suffered a broken left collar bone, shoulder and several ribs as well as a bruised spleen and liver when he came off Miss Promiscuity in last month's Robert Sangster Stakes at Morphettville.

He is expected to be sidelined until at least the end of the season on July 31.

An inquiry by South Australian stewards found Nolen came off when Miss Promiscuity knuckled around the 700m mark.

The jockey was struck by Pittsburgh Flyer who was unable to avoid him as he lay on the ground.

Stewards said no other rider was to blame for the incident.

Just 40 minutes earlier, Nolen had ridden his first Group One winner since returning from a seven-month recuperation from back surgery when he steered Abbie Marie to win the Australasian Oaks.

Jake Noonan, who won the Sangster on Precious Gem, is also on the injured list after breaking his leg in a fall at Pakenham on Sunday.

Noonan is expected to be out for up to three months.