NFL Champions 1920-2015. From 1920-1931, the NFL champion was determined by a team's win-loss percentage. In 1932, a playoff game was needed to determine the championship. Starting in 1933, the NFL split into two divisions and a championship game was played between the two division winners. The AFL and NFL announced that the two leagues would merge in 1970. The Super Bowl started to determine the world champions. The game featured the champion of each league.