Coordinator changes and heavy player personnel losses made it a spring of uncertainty for the top Big Ten defenses.
Start with Wisconsin.
The Badgers have been in the national top five in total defense three straight years.
They must replace eight of their top 10 tacklers.
Penn State has a new coordinator in Manny Diaz.
The former Miami coach must fill spots of as many as six players who could be drafted.
Defending conference champion Michigan must replace seven starters.
Ohio State also is retooling its defense after it got exposed against Oregon and in a 42-27 loss to Michigan.
