The final unit preview seems to be pretty straightforward. Purdue returns both kickers and even with some new faces there, it would be a surprise to see either lose their jobs. The biggest loss is Raheem Mostert. The school's best ever kick returner in terms of total yards is now trying to make it with the Philadelphia Eagles, while Akeem Hunt, who was pretty damn good in his own right, is in the same boat with the New York Giants.
The largest area of improvement needs to be kick coverage. Either Purdue needs to kick the ball out of the end zone or actually tackle a returner, because the coverage units were just plain bad:
But special teams is going to only be so much of a strength if kickoffs and punts are a drain on field position.