Year four is often a pivotal season for a head coach, particularly in the cutthroat SEC. By then, the roster overwhelmingly consists of players that he evaluated, recruited and signed.
With that being the case, you don’t have to worry as much about whether players he inherited from the previous staff make him look like a better coach than he actually is or a worse coach than he actually is. There’s no mistaking who gets the credit or the blame for the program’s results any longer.
So, year four is often viewed as a snapshot of what fans can expect from the program moving forward under that coach’s guidance.