LOS ANGELES -- The most valuable lesson Aaron Corp has learned in his two years as a USC quarterback was not found between the covers of his playbook. That's saying something, because Corp's knowledge of the Trojans' offense is the vehicle he has ridden to the front of the three-man race to replace Mark Sanchez.
"He knows everything," quarterbacks coach Jeremy Bates said last week. "He can get in and out of the huddle, take care of the other 10 players, get them in the right position. He understands all the progressions. His mind is working extremely fast right now. He knows 1-2-3 and he can get to 4 and 5."
Throughout spring practice, Corp made his reads, put the ball where only his color jerseys could catch it and obeyed the first rule of quarterbacks and physicians: Do no harm.
In fact, when head coach Pete Carroll announced April 21 that Corp would start the spring game and enter fall practice on the first team, Corp had not thrown an interception in any of 13 spring practices.
"I pride myself on knowing the defense and knowing where the ball is supposed to be in that defense," Corp said. "I think that's what being a quarterback is all about, the mental aspect of it. Because you see guys in the NFL obviously who have big arms. But you look at guys like Matt Hasselbeck or guys who came out of the sixth round, they are successful because they're so smart."
Under Carroll, the Trojans attract so much attention in Los Angeles you'd think they practice on a red carpet. But this quarterback race has had nothing to do with star power. The biggest name among the candidates, redshirt junior Mitch Mustain, the former Arkansas transfer, fell to third string.
The most magnetic candidate is freshman Matt Barkley, who enrolled in January and grasped the Trojans' offense with the ease and confidence of a veteran. In the hierarchy of college athletics, that's close to unprecedented. Most freshmen, if they have the guts to speak at all, are quickly told to shut up, expletives added at no extra charge.
Carroll, rarely at a loss for words, gropes for the description that would explain how far Barkley has traveled in so short a time. In one 24-hour period last week, Carroll used "amazing," "great surprise" and "extraordinarily gifted" to describe the rise of Barkley. He is 18, already 6-foot-3, 220 pounds, and has "star" written all over him.
Corp might not be a star, but he is the starter. Corp doesn't attract the spotlight in the same way. At 6-4, 195, his body presents more angles than a geometry quiz.
"Yeah, I still got room for development. I'm still skinny," he said.
Many young quarterbacks start out by seeing how hard they can throw, and only then do they learn the nuance of touch. Not Corp.
"When I first came in, I didn't have a strong arm at all," he said. "I didn't think I was the guy who was going to think I could force anything. So I think that helped me. Then my arm kind of developed, got a little stronger. I could start making some throws I wasn't able to before. That actually kind of helped me before, not to force balls."
He didn't win the job because of his game experience. Corp threw four passes as a redshirt freshman in 2008. He started out as the backup to Sanchez, but shortly after the season began, he slid to third on the depth chart behind Mustain. Corp stayed there throughout the regular season.
That brings us to the valuable lesson. Asked why he lost the job as backup, Corp smiled an embarrassed smile and said "I kind of got lazy, to be honest."
Last season, three weeks before the opener at Virginia, Sanchez dislocated his left kneecap in practice. Corp practiced with a maturity that belied the fact he had been on campus only a year.
"There was a real opportunity for me to play the first game," Corp recalled. "I really tried to push myself."
Corp practiced so well he moved ahead of Mustain. But the Monday before the opener, Sanchez put on his cleats, tested his knee and reclaimed his starting job. That's when Corp reclaimed the immaturity he had appeared to outgrow.
"When Mark came back it was, 'OK, Mark is gonna play,'" Corp said.
"And then, 'OK, Mark is gonna play. I don't have to study as much film.'"
Corp took the road traveled by most underclassmen. He felt safe in the shadow of a more experienced teammate. So he slacked off. Before September ended, Mustain passed him on the depth chart.
Hello, reality. Hello, lesson.
"It was kind of a grind through the rest of the season," Corp said.
Most coaches use the 10 practices allowed for bowl preparation as a pseudo-spring. The second time that opportunity opened a door for Corp, he burst through it. Before the Rose Bowl, Corp performed better than Mustain and moved back to second-team quarterback.
When Sanchez announced in January that he would forego his senior season to play in the NFL, he surprised Carroll and most everyone else, Corp included.
"He sent me a text message the day before," Corp said. "I thought he would be back next year. I'm gratified for the opportunity."
Corp played in the spring game Saturday at Los Angeles Memorial Coliseum pretty much as he played throughout spring practice. He completed 14 of 23 passes for 157 yards and one touchdown. He led the Cardinal team to a touchdown and two field goals in a 16-10 victory over the White.
Corp didn't throw a pick, which extended his streak of practices without a turnover to, uh, one. Naturally, two days earlier, on one of the first plays in the first practice after Corp moved to the top rung of the depth chart, he threw a pick.
Defensive tackle Jurrell Casey tipped a Corp pass at the line, gathered in the ball and rumbled downfield. Corp dived at Casey, who outweighs him by 85 pounds. Luckily for the Trojans, Corp missed.
"I'm not a very good tackler," he said. "I don't really work on that too much."
Ivan Maisel is a senior writer for ESPN.com. Send your questions and comments to Ivan at Ivan.Maisel@ESPN3.com. His book, "The Maisel Report: College Football's Most Overrated & Underrated Players, Coaches, Teams, and Traditions," is on sale now. For more information, go to TheMaiselReport.com.