TCU opened spring practice Friday for the second time as a Big 12 member. Let's take a closer look.

Schedule: The Frogs began spring practice on Friday, which will be the first of 15 NCAA-allowed practices. TCU rarely holds a spring game, and will not hold one this season.

What's new: Very, very little, especially on defense. TCU lost coach Randy Shannon to Arkansas this offseason, but returns 15 starters from last year's seven-win team, second most in the Big 12 (only Texas has more) and 24th nationally. Shannon was replaced by DeMontie Cross, who comes to TCU from Kansas' staff under Charlie Weis. On the field, there are big pieces that must be replaced (defensive end Stansly Maponga and wide receiver Josh Boyce), but the Frogs will largely have the same personnel next season as they had in 2012.

All eyes on: Quarterback Casey Pachall. He's the biggest story of spring in the Big 12 by far. Pachall was one of the Big 12's best at the position a year ago, but left the team after a DUI arrest to seek treatment for drug and alcohol addiction. He's back on the team now and TCU's Big 12 title hopes hinge on him returning to form after time away from the game. He's also going to be watched closely when he's off the field. Will he be able to make the necessary adjustments to make his new lifestyle a permanent, healthy change?

New faces: TCU will be welcoming three early enrollees this spring, headlined by quarterback Zach Allen, the nation's No. 56 pocket passer. He'll be joined by tight end Bryson Burtnett from Springtown, Texas, and Georgia offensive tackle Eason Fromayan. There aren't many immediate contributors in that group, I'd say, but it's always good for freshmen to get a head start in spring practice.

Question marks: We've mentioned this previously, but you can't underestimate the importance of offensive line play in the Big 12. It can make any offense look great, and TCU will have to replace two of its best players on the line in guard Blaize Foltz and center James Fry. Sorting out their replacements will be a primary objective this spring.

Position battle: TCU's running back spot is going to be really strong and intriguing. I expect all the backs to get carries in the fall, Waymon James will be returning from a knee injury and trying to hold off B.J. Catalon to retain his starting position. What people really want to see, though, is Nebraska transfer Aaron Green's debut as an eligible player. He was one of the nation's top 10 prospects in the 2010 recruiting class and sat out last season after coming home to Texas.