Why did the defense not progress?

I struggled with the wording, and might have said “regress” instead. We were exposed in the Arkansas game; busts in our coverage such as a wheel route and/or swing pass to the rb, as well a tight end crossing route we just couldn’t defend against. Injuries aside, one should improve their individual play over the football year, and we never did. Our linebackers were lost most games, and our secondary was confused too many times. What is the solution here? Yes, getting players back from injury will help, but something deeper is not right. Roll Tide anyway!