Michigan is seeing one of its best defensive tackles in recent memory, Mike Martin, graduate. It also watches Ryan Van Bergen and Will Heininger, who rotated between end and tackle throughout the season, leave.
So while the Wolverines have some depth returning at one defensive end slot, they have nothing at defensive tackle. And considering how much of Michigan's run defense and pass rush came out of what Martin was able to do on the line, it is the Wolverines' biggest issue entering the spring.
So what happens?