This story is part of USA TODAY Sports' 25 days to college football countdown.
A fixture in the race for the College Football Playoff, Oklahoma's championship hopes feel even more legitimate thanks to the growth of a defense that is suddenly an asset, not a liability.
Last season saw the Sooners hold five straight conference opponents to 400 or fewer yards of offense, the program's longest such streak since 2012. After giving up 40 points per game against its first three Big 12 foes, OU allowed just 17 points per game and 4.2 yards per play in closing 7-0, capped by a 55-20 win against Florida in the Cotton Bowl.