An incident in the starting stalls at Canterbury has left champion jockey Nash Rawiller sore and sorry but it could have been much worse.

Rawiller's mount in the TAB Rewards Handicap, Happy Meteor, reared in the barriers after being stirred up by rival Castigate who was restless in the gates.

Happy Meteor hit his head when he reared and slid to the ground, pinning Rawiller between him and the back of the stalls as he struggled to regain his feet.

Rawiller suffered bruising to his lower back but assistant starter Peter Svendsen put the incident into perspective when he said: "He's lucky to be alive.

"The horse pinned Nash between it and the back of the gate and the horse itself then spun around and came at Nash front-on before we could get them out.

"We're lucky we've got barrier attendants who are trained to get guys out in a situation like that and the fact the horse was a bit dazed probably stopped it thrashing around more."

Svendsen said Happy Meteor's face "with the bit in its mouth" was just inches from the pinned Rawiller.

The premier hoop, who came with a late-season surge to claim last season's Sydney jockeys' title and has continued that form into the new season, was stood down from his remaining rides on Wednesday's program.

He acknowledged the situation in the barriers had the potential to have been serious.

"It was a pretty frightening situation actually," Rawiller said.

"I am lucky the barrier guys were there."

Both horse and jockey ended up on the ground before the barrier officials were able to drag Rawiller out of danger.

Stewards open an inquiry and ordered Happy Meteor, who was the favourite, back to the barrier trials.

Castigate had a warning placed on her but doesn't have to trial.