UCLA's Myles Jack lost for season due to knee injury

UCLA star LB Myles Jack is out for the season due to a knee injury, coach Jim Mora confirmed Wednesday morning. 

Jack hurt his knee during a non-contact drill near the end of Tuesday's practice, and he had surgery that evening.

The 20-year-old junior, a three-year starter, is the team's No. 3 tackler and helped seal the Bruins' win over BYU last week with an interception in the final seconds of the game. UCLA will visit unbeaten Arizona on Saturday in Tucson.

The Bruins already lost standout defensive lineman Eddie Vanderdoes (knee) and cornerback Fabian Moreau (foot) for the season.

Two years ago, Jack had his national coming-out party at Arizona, when he did double duty as a tailback and linebacker. He rushed for 120 yards on six carries, including a 66-yard touchdown, and made eight tackles, recovered a fumble and broke up two passes in a 31-26 Bruins victory.

Look for juniors Jayon Brown and Cameron Judge to get reps with Jack out at linebacker.

The Associated Press contributed to this report.