Biggest shoes to fill: Arizona

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.

In alphabetical order, we will survey each Pac-12 team’s most notable void.

Biggest shoes: Running back Ka'Deem Carey

Carey was the nation's best running back in 2013. A two-time consensus All-American and the Pac-12's Offensive Player of the Year, he rushed for 1,885 yards and scored 19 touchdowns last fall. He ranked second in the nation with 157.1 yards per game. He completed his career by topping 100 yards in 16 consecutive games, a Pac-12 record and a streak that hasn't been accomplished by any other back in a decade. He is Arizona’s career rushing leader (4,232 yards) and ranks seventh in Pac-12 history. He owns or shares 26 Arizona single-game, season and career records. He's a physical, instinctive runner who also was a good receiver (he caught 26 passes for 173 yards and a score) and capable blocker in pass protection.

Stepping in: Probably a committee of three or so guys

Not only do the Wildcats lose Carey, they lose his capable backup Daniel Jenkins, who rushed for 411 yards last year. The one returning RB with game experience, Jared Baker, tore his ACL in the regular-season finale. Moreover, true freshman Jonathan Haden, who had enrolled early so he could participate in spring practices, still hasn't joined the competition because of an NCAA Clearinghouse issue. So far the spring battle has been between redshirt freshmen Pierre Cormier, Zach Green and senior Terris Jones-Grigsby. True freshman Nick Wilson will enter the fray in August. Further, what has become clear is coach Rich Rodriguez isn't afraid to tap into his deep, speedy crew of receivers for help running the ball. Expect both Davonte' Neal and T.J. Johnson to get looks in the backfield as well as out wide.