Complex sentence: The game was the first postseason bowl game in which the players were required to play on both the offense and defense, under the NCAA's newly-instituted "one-platoon" rules that limited player substitutions.
Split into simpler sentences: The game was the first postseason bowl game in which the players were required to play on both the offense and defense. This was a result of the NCAA's newly-instituted "one-platoon" rules that limited player substitutions.