American jockey Gary Stevens suffered a collapsed lung but broke no bones when he fell in Saturday's Arlington Million.
Stevens sustained the injuries when Storming Home veered out sharply after spooking a few yards before the finish line, throwing the rider to the turf where he was then stepped on by one of the horses behind.
Stevens is being treated in Chicago's North Shore Hospital but he is expected to be released on Wednesday.
His riding agent, Craig O'Bryan, told www.bloodhorse.com: "He's still in the hospital in Chicago and they're doing an MRI as a precaution because he's extremely sore, but as of now it appears he was very lucky and didn't break anything."
Stevens is hoping to be back in action on Candy Ride in Sunday's Pacific Classic.