Oklahoma has high expectations — per usual — heading into the 2018 season, and there's plenty of reason to think it will once again sit atop the Big 12 standings in December.
But the Sooners also have quite a bit to replace on both sides of the ball, including the 2017 Heisman Trophy winner and their unquestioned leader. There are still lingering question marks with the defense, both in personnel and in scheme. Important players from a year ago have no obvious replacements.
Here are five reasons OU fans could be pessimistic about the upcoming 2018 football season:
Note: This is a part of a series previewing Oklahoma's 2018 season.