Complex sentence: Castillo suffered a cut due to a headbutt, and the fight was stopped in the 6th round, and, by rule when a headbutt is ruled to be unintentional, the fight went to the scorecards.
Split into simpler sentences: Castillo suffered a cut due to a headbutt, and the fight was stopped in the 6th round. By rule when a headbutt is ruled to be unintentional, the fight went to the scorecards.