TEMPE, Ariz. (AP) -- Arizona Cardinals rookie Tyrann Mathieu will have surgery Friday to repair torn ligaments in his left knee.
Mathieu, speaking informally to a small group of reporters at team headquarters Thursday, said he knows it will be difficult to watch the team play for the remainder of the season.
''I felt like I disappointed my team,'' he said. ''I can't be out there with those guys. We're in the playoff chase, and you just want to be out there and help those guys. Knowing that you can't be out there to help them is the frustrating thing.''
It is the first serious injury of Mathieu's career, and he says he will do his rehab work in Arizona.
The young safety, whose college career at LSU was cut short by marijuana-related issues, has developed a strong support system in Arizona.
Mathieu tore his ACL and LCS when he was hit while returning a free kick following a safety in the Cardinals' 30-10 victory over St. Louis last Sunday. He jogged toward the sideline, then his knee buckled and he collapsed on the field.
''I was a bit scared,'' Mathieu said. ''I haven't been injured. I twisted my ankle and sprained my ankle a few times, but I never had a serious injury. Once my knee buckled, I knew it was a serious injury.''
He said he has been listening to teammates who have gone through the same sort of injury.
''They say the more work you put into it, the better the results,'' Mathieu said.
The 5-foot-9 dynamo was having a terrific rookie season, playing on nearly every defensive snap. He is second on the team in tackles (63) and solo tackles (56). He also had two interceptions, a sack, a forced fumble and three quarterback hits.
''I know I played pretty good,'' Mathieu said. ''I think I set a pretty good standard for rookies coming in at defensive back for the Cardinals this year. I didn't feel like I played my best. I felt like my best was still ahead of me. I've got some months to reflect on it and hopefully motivate me to go out there and set some records next year.''
Coach Bruce Arians has downplayed any chance Mathieu could be ready by training camp next year.
''I head that,'' Mathieu said. ''I don't know. Coach is just being generous. He doesn't want to rush me back, but hopefully everything goes well and goes fast. Hopefully, I can come back like A.P. (Adrian Peterson).''
AP NFL website: www.pro32.ap.org