Lee is a projected first round pick and multiple mock drafts have him slated to go 15th to the Pittsburgh Steelers.
In 2012, Lee caught 118 passes for 1,721 yards and 14 touchdowns becoming the first USC Trojan to win the Biletnikoff Award.
After winning that award as the nation's best wide receiver and taking out an insurance policy before the start of his junior season, it was viewed as a given 2013 would be the last for Lee at USC.
However, his decision wasn't that cut and dry.
"It's not that easy," a source close to the situation told FOXSportsWest.com prior to Lee's announcement.
Lee seriously contemplated returning for his senior season, the source said.
In the end, he used Friday to thank the "Trojan Family" for all they'd done for him throughout his three seasons in Cardinal and Gold.
He finished his junior and final season at USC with 57 catches for 791 yards and four touchdowns in a injury-plagued season. He didn't leave, however, without giving USC fans something to remember him by with seven catches for 118 yards and two touchdowns in USC's 45-20 Las Vegas Bowl win over Fresno State.
Some of Lee's highlights at USC include his Pac-12 record 345 receiving yards at Arizona in 2012. He was named Pac-12 Offensive Player of the Year that season and was a unanimous All-American.
Lee joins safety Dion Bailey, George Uko, and Marcus Martin as Trojans who decided to leave school early and enter this year's NFL Draft.