Complex sentence: Because only allowing divisional winners in the playoffs would make an odd number of playoff teams in each league, three, the league also added wild-cards to each league, imitating the original post-merger NFL system.
Split into simpler sentences: Because only allowing divisional winners in the post-season would make an odd number of teams in each league, three. To rectify the odd number of teams the league added wild-cards to each league, imitating the original post-merger NFL system.