Complex sentence: Since the ACC adopted divisional format for football, one of these two teams had represented the ACC Coastal Division in every ACC Championship Game, the only exception being the 2013 season when Duke won the Coastal outright.
Split into simpler sentences: Since the ACC adopted divisional format for football, one of these two teams had represented the ACC Coastal Division in every ACC Championship Game. The only exception being the 2013 season when Duke won the Coastal outright.