With the advent of the new College Football Playoff, the SEC voted last year to require their members to play a Power Five opponent (ACC, Big Ten, Big 12, Pac-12) in its non-conference schedule beginning in 2016.
The decision was prompted by the Playoff system placing an increased emphasis on strength of schedule. Since the Big12 and Pac12, play nine conference games, the SEC felt like it needed to be able to show they equally play just as many Power Five schools – hence the need for the new rule.
The SEC considered going to a nine game schedule but sentiment prevailed that the league already has a tough enough schedule without adding another SEC opponent.