Complex sentence: Sources indicate the game was a violent one with players often ending up on the ground, in Greece, a spectator (of the Greek form of the game) once had his leg broken when he got caught in the middle of play.
Split into simpler sentences: Sources indicate the game was a violent one with players often ending up on the ground. In Greece, a spectator (of the Greek form of the game) once had his leg broken when he got caught in the middle of play.