Jeff Zelevansky/Getty Images(TEMPE, Ariz.) — Arizona Cardinals safety Tyrann Mathieu is out for the season after tearing the ACL and LCL in his left knee during the Cardinals victory over the St. Louis Rams Sunday .
Mathieu injured the knee in the third quarter while returning a free kick. After the play he fell to the ground and eventually was carted off the field.
Mathieu had an MRI on Monday that revealed the injury. He won’t be able to have surgery until the LCL begins to heal.
The 21-year-old rookie out of LSU was a third round pick of the Cardinals in this year’s draft.
Mathieu has 68 tackles, nine passes defended, two interceptions, one forced fumble and a sack this season. He also was named October’s NFC Rookie of the Month.