Background and college
Born November 11, 1986 in Long Beach, California, Sanchez attended Santa Margarita Catholic High School for two years. His first pass attempt in high school, as a sophomore, was a 55-yard touchdown completion. While at Santa Margarita, he served as ball boy for future USC Heisman Trophy winner and future NFL quarterback Carson Palmer. He then transferred to Mission Viejo High School to play for his high school quarterback guru, Bob Johnson; Johnson, father of former USC and NFL quarterback Rob Johnson, was also the private coach for Palmer. At Mission Viejo he threw for 2,600 yards, 29 touchdowns, and only four interceptions as a junior. With a 75 percent completion rate, he rushed for 90 yards and had a receiving touchdown on a reverse throwback. Sanchez was named a first team all-league, county, and CIF selection. Sanchez carried a 3.7 GPA, and was the president of the student government and captain of the basketball team. As a senior, Sanchez completed 114 of 186 passes for 1,746 yards, 16 touchdowns and 2 interceptions, leading his team to a state championship. With Sanchez as quarterback, the Mission Viejo Diablos went 27–1.
In 2004, Sanchez was named high school "Player of the Year" by several major college recruiting services and participated in the 2005 U.S. Army All-American Bowl. He chose to attend USC. In 2005 Sanchez did not play during his freshman year, and instead took a redshirt season. For the 2006 season, Sanchez competed for the starting position; however, once junior John David Booty underwent back surgery after the first day of spring practice, Sanchez ran the first-team offense during the spring as Booty recuperated. As a redshirt freshman, Sanchez served as the back-up quarterback to Booty, seeing playing time in three games. He passed for 63 yards and no touchdowns with one interception.
In fall practice before the 2007 season, Sanchez broke the thumb in his throwing hand, missing the first game against Idaho; he returned the following week and the redshirt sophomore again served as the primary backup to Booty, though he would start a few ganmes mid season. During the first week of the 2008 fall camp, Sanchez suffered a dislocated left kneecap while warming up for practice; trainers were able to immediately put the kneecap back into place. After missing nearly three weeks, Sanchez was cleared to play in the opener against Virginia on the final scrimmage of fall camp.
Sanchez starting all 13 games at quarterback, the Trojans ended the season 12–1 and ranked No. 2 in the Coaches Poll and No. 3 in the AP Poll. Sanchez won the 2009 Rose Bowl Offensive MVP of the game; his 413 passing yards ranked fourth in Trojans history and were the highest since Carson Palmer threw for 425 against Notre Dame in 2002. He finished the season with 34 scoring passes, second in school history behind Matt Leinart's 38 in 2003. Sanchez ended his redshirt junior season with 3,207 yards passing, 34 touchdowns and 10 interceptions.
After the Rose Bowl, Sanchez said it would be "hard" to leave USC for the NFL and "probably couldn't do it; he would have entered his redshirt senior year if he had stayed. On January 15, Sanchez announced his plans to forgo his final year of college eligibility and enter the 2009 NFL Draft; he plans to continue as a USC student and finish his degree in the Spring of 2009 while preparing for the draft. During the press conference, Carroll made it clear that he did not agree with Sanchez' decision, and that he advised him of the low success-rate of quarterbacks who left the college game early to enter the NFL. Despite the public disagreement, the two remained close afterward. Sanchez was the first USC quarterback to turn pro before exhausting his eligibility since Todd Marinovich did so after the 1990 season.
As a Jet
Sanchez was taken by the Jets with the fifth overall pick of the 2009 NFL Draft, making him the first quarterback selected by the Jets in the first round since Chad Pennington was picked 18th overall in 2000. In order to select Sanchez, the Jets made the biggest draft-day trade in their history to move up to the fifth selection. The pick was lauded at the time it was made as a good value for team and player.
On June 10, Sanchez signed a five-year contract with the Jets worth $50 million, with $28 million in guarantees. It is the largest contract the Jets signed with a player in franchise history. He was also the second draft pick signed from the 2009 draft.
Heading into into his rookie training camp, Sanchez was listed as the #2 quarterback behind veteran Kellen Clemens. Jets Head Coach Rex Ryan noted that he viewed training camp as an open competition between the two for the eventual starting position for the 2009 season. On August 26, 2009 Sanchez was named the starter for the Jets, beating out Clemens for the job.