Coming off a record-setting Rose Bowl, the Southern California quarterback will skip his senior season to enter the NFL draft - going against the advice of coach Pete Carroll.
Sanchez, a fourth-year junior, announced his plans at a campus news conference Thursday, the deadline for underclassmen to declare for the draft.
The past three stars who played quarterback at USC under Carroll stayed for their senior seasons, and the former NFL coach thought Sanchez should do the same.
Carroll tried to convince Sanchez that another year of college experience would help him in the pro game, but Sanchez said he had carefully weighed all the considerations before deciding to leave.
"It has been my dream since I was just a little kid to play in the NFL and thanks to this great academic institution and football program, I have the opportunity to realize that dream," said Sanchez, dapperly dressed in a business suit.
"It was with a heavy heart that I say goodbye to this university. But I can't tell you how excited I am for this dream to come true."
Heisman Trophy winners Carson Palmer and Matt Leinart, along with John David Booty, all returned for their final year of eligibility with the Trojans. Palmer was the first overall pick in the 2002 NFL draft and Leinart was selected 10th in 2005.
Carroll, who said he considers Sanchez as talented as any of those three, discussed the pros and cons with him.
"We've talked at great depth and great length. We've covered this from A to Z ... going until late last night," Carroll said. "We don't see this decision the same. (But) I'm thrilled for Mark. For any of our kids to live the dream and do what they want to do with their football career, this is a great place to do this."
Because 2008 Heisman winner Sam Bradford of Oklahoma, 2007 Heisman winner Tim Tebow of Florida and Texas star Colt McCoy all plan to return to school next season, Sanchez and Georgia's Matthew Stafford - another junior coming out early - likely will be the top quarterback prospects in the draft.
Mitch Mustain, who transferred from Arkansas after going 8-0 in games he started as a Razorbacks freshman in 2006, is expected to compete with Aaron Corp, Garrett Green and incoming freshman Matt Barkley for the Trojans' starting job.
Carroll, a former head coach with the New York Jets and New England Patriots, thinks another year of college experience would have greatly benefited Sanchez, who started at USC for only one full season.
"Mark is going against the grain on this decision and he knows that. He knows that coming out early is a tremendous challenge for a quarterback and the statistics don't back up that it's easy to be successful in the way that he's going about it," Carroll said.
"We've seen successes and we've seen guys come up short on this deal. We hope this works out beautifully for Mark and his family."
Carroll isn't selling Sanchez short.
"He's a competitive guy, a guy that's willing to take on this challenge in a way that he's going to make it happen," the coach said. "Mark clearly has the potential to be as good as any of those guys we've had. We saw it early on.
"All it is is an experience issue."
Sanchez ended his college career with his finest game. The 6-foot-3, 225-pounder went 28-for-35 against Penn State, setting a Rose Bowl record by completing 80 percent of his passes. He threw for 413 yards and four touchdowns, and also ran for a score in the Trojans' 38-24 victory.
Sanchez led the Trojans to a 12-1 record and No. 3 national ranking last season after going 2-1 the previous year while Booty was hurt.
A high school star in nearby Mission Viejo who redshirted at USC in 2005, Sanchez finished last season with 3,207 yards passing, 34 touchdowns and 10 interceptions. He threw for 695 yards and seven touchdowns with five interceptions in 2007.
Sanchez said he came to USC to get an education, to compete at the highest college level and earn a chance to play in the NFL.
"I'm proud to say that this spring, I'll have the opportunity to do both," said Sanchez, on track to receive his degree in communications.
His father, Nick, said he had mixed emotions about his son's decision to enter the draft.
"As a parent, I'd like for him to stay in school for another 10 years," he said. "But it's great to see a young man trying to live his dream."
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