Mark J. Terrill, AP
UCLA linebacker Myles Jack runs during the second half of an NCAA college football game against Memphis, Saturday, Sept. 6, 2014, in Pasadena, Calif. UCLA won 42-35. (AP Photo/Mark J. Terrill)

LOS ANGELES — Injured UCLA linebacker Myles Jack has dropped out of school, and he plans to enter the NFL draft next year.

UCLA coach Jim Mora expressed trepidation about Jack's decision when he announced it Tuesday.

Jack is out for the rest of his junior season after tearing a ligament in his knee during a non-contact drill in practice last month. He was a starting linebacker and a frequent running back for the Bruins during his first two seasons.

Mora says Jack and his family had already decided Jack should drop out of school to prepare for the NFL before speaking to Mora. The veteran NFL coach says the move is "very risky."

Jack played two full seasons at UCLA. He was the Pac-12's freshman of the year on offense and defense in 2013.