dog injurys are not common, Happys sister got a concussion when another dog that was supposed to rerun got away from his handler too soon and they had a head on collision, there are always vets around at tourniments just in case as many vets participate in flyball themselves, when the concussion happend we actually had a vet on our team. your not putting him in danger with flyball dont worry, most flyball dogs that get injured, dont get it from playing flyball, most often its in the owners own backyard and totally unrelated to the sport.