From the outset, this was going to be a concern. Tennessee football fans remember the 2012 season, the one time the Vols made a transition to a 3-4. It resulted in one of the worst defenses in school history.
The root of that horrendous defense came in the secondary, which looked awful. So when Jeremy Pruitt took the job and confirmed that he and Kevin Sherrer would install that 3-4 system again, there was already reason to believe that the Vols would struggle in the secondary this year.
Spring ball pretty much confirmed that. The first-team secondary was awful in the spring game, and Pruitt was either praising the offense or scolding the defense, in particular the secondary, for most of his press conferences in the spring.