TEMPE, Ariz. --
felt something out of the ordinary as soon as he was tackled while returning a kick in the third quarter of Sunday's win over the Rams at University of Phoenix Stadium.
"I felt it when the guy kind of jumped on my leg, but I felt like I could run it off," Mathieu said Thursday at the team's Tempe complex. "Once I got to the sideline, it just buckled.
"I've twisted my ankle, sprained my ankle a few times, but I haven’t had a serious injury. Once my knee buckled, I knew it was a serious injury."