One of the more interesting aspects of this gig, over time, is watching the arcs of certain players ebb and flow, especially high profile guys you're introduced to before they even take a college snap. Mitch Mustain wore that label prominently as one of the five-star gems of the class of 2006 and the most sought-after signee in Arkansas history, and soon after as the unwitting catalyst of the petty soap opera that effectively ripped the program apart. Three years later and half a continent away, staring at the only real window he'll have to fulfill his potential at USC, the Orange County Register says Mustain's prospects have clearly ebbed:

What began as a three-man competition to become USC’s starting quarterback in 2009 is now a two-man race.

Aaron Corp and Matt Barkley are the two. Mitch Mustain is the odd man out.
[...]
Whatever magic Mustain had as a national high school player of the year hasn’t materialized since he became a Trojan. Two theories why: (1) The adjustment from a shotgun spread attack to USC’s pro-style offense is more difficult than you might think; (2) the coaches have so ingrained in Mustain’s head to not throw interceptions that he has lost his aggressiveness.
[...]
His numbers in the two scrimmages so far bear this out as well: Mustain is 10 of 18 for 64 yards. That’s less than 4 yards per attempt, and it’s not indicative of a quarterback who is seeing receivers come open down the field and delivering the ball to them.

USC's quarterback competition has been considered somewhat in the tank for sophomore Aaron Corp for a couple weeks now, but it hasn't been clear just how far behind Mustain has actually fallen; the L.A. Daily News' Scott Wolf backs up the point today, writing that Mustain has been "cubby-holed into the backup role" in the name of developing the new new blood, Barkley. Mustain could have transferred almost anywhere (save Oklahoma, with Sam Bradford, and maybe Notre Dame) and been virtually assured of starting this year or next year as a fifth-year senior. Instead, he elected to compete forever and will apparently spend his last two years of eligibility either a) Sitting on the Trojan bench, playing out the string and e-mailing pro scouts pictures of Matt Cassell, or b) Trying to get one good year out of a third school, preferably one not rife with hateful, insulting boosters or stocked with another pair of up-and-coming five stars.

The latter is what makes Mustain's passage into obscurity more of an issue of bad timing than busting out: If the roles were reversed, the same lament could be written about the lost talents of Corp or Barkley, fellow blue chips who offer coaches an interesting contrast over the next two weeks. If Mustain was too conservative, Barkley is the anti-Mustain, drawing praise as a big-play gunslinger -- he was 10 of 13 for 195 yards and three touchdowns during last Saturday's scrimmage, his first in the L.A. Coliseum -- at the same time everyone who watches him frets over the number of interceptions he throws. Corp is somewhere in the middle, balancing Mustain's experience (both are entering their third year in the system) and extreme prudence (Corp hasn't thrown a single interception through eight practices this spring) with Barkley's future (Corp could be a three-year starter if he wins the job, as expected) and adding a little athleticism to the mix.

Which is why Corp seems destined to win the job unless Barkley explodes -- for his effusive praise about Barkley's adjustment to college and ability to pick up the offense, Pete Carroll's top priority has always been turnovers, and by all accounts the freshman has been committing too many of them. And, you know, he's a freshman; paying your dues and all that. But if Barkley continues to compete and somehow does win the job, there's no question about the fate of his talent, is there? It's got to be four Heisman Trophies, right? Right?