When a college football program goes through a coaching change, it’s common for there to be a mismatch between the inherited roster and the new scheme. For example, a pro-style offense might be loaded up with pocket passing QBs and blocking TEs. If a new coach were to comes in and installs a spread offense, there would likely be some growing pains.
Similar roster friction can occur on defense. If a team has played 4-3 defense, the roster will be made up of players recruited for that scheme. If a new coach were to install a 3-4 defense, there could be problems.