Starters in, starters out. That's college football. Players' eligibility expires and they leave for the rest of their lives, whether that includes the NFL or not.

And they leave behind shoes of various sizes that need to be filled.

Our concern with this series? The biggest shoes -- in some cases Shaq-like size 23s.

We start with Arizona.

Big shoes: WR Juron Criner.

This isn't just about Criner -- the Wildcats lose a ton of production at receiver -- but the 6-foot-4, 215-pound Criner caught 209 passes and scored 32 TDs over the past four years. He's been the Wildcats go-to receiver for two years. Further, new coach Rich Rodriguez is almost completely rebuilding the receiving corps as he installs his spread-option offense. Arizona's top three receivers from 2011 are gone and that absence grows to four of the top five if you include departed running back Keola Antolin. Also, seventh-leading receiver Richard Morrison is playing QB this spring.

Stepping in: WR Dan Buckner

The first question is whether Dan Buckner can step up. The hyped, 6-foot-4 Texas transfer had a decent 2011, ranking fourth on the team with 42 receptions for 606 yards and two touchdowns, but he needs to be more consistent in order to step into Criner's shoes. There are other options, too, including 6-foot-3 sophomore Austin Hill. Or perhaps it will be Tyler Slavin or Garic Wharton? Or perhaps Rodriguez's run-first offense won't throw the ball enough for these shoes to be so critical?