"The time is right," McKnight said in the report. "This was my first healthy season and I really don't want to come back and risk injury."
In 2009 McKnight had his most productive season as a Trojan, rushing for 1,014 yards and 8 touchdowns while averaging 6.2 yards per carry.
"If I would have come back it would have been to pursue the Heisman," McKnight said.
McKnight was held out of USC's 24-13 victory over Boston College in the Emerald Bowl because the university was investigating his use of an SUV that was owned by a Santa Monica businessman. He joined the team in San Francisco but wasn't cleared by the compliance official before the start of the game.
With the loss of McKnight, Allen Bradford will enter spring practice as the No.1 tailback on the depth chart with C.J. Gable the likely No.2, if he decided to return in 2010. Marc Tyler and Curtis McNeal would also be in the mix for playing time.
Joe McKnight has decided to enter the NFL draft.
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