CHARLOTTE - Middle linebacker Ryan Kalil, the Panthers' leading tackler each of the past four seasons, tore his left Achilles tendon in Sunday's game at Arizona and will be lost for the season, head coach Ron Rivera announced Monday.
Beason suffered the injury early in the second half of Carolina's 28-21 loss, falling to the ground as he tried to catch up with tight end Jeff King in open field on a 48-yard pass play.
Beason was carted off the field and didn't return. An MRI on Monday afternoon confirmed the extent of his injury.
Rivera said Beason would undergo surgery sometime in the next few days.
"It's such a freak thing," Panthers defensive coordinator Sean McDermott said. "This game is so fast and physical. I've got to give Jon credit - he was running a hundred miles an hour when he went down.
"It's just a shame. He's a warrior, and I'll take those guys seven days a week."
Dan Connor, who started eight games in the middle last season before a hip injury ended his season, took over for Beason on Sunday and will get the call when the Green Bay Packers visit Bank of America Stadium on Sunday. The Panthers also have veteran Omar Gaither, who saw significant time in the middle in five seasons with the Philadelphia Eagles.
"We kept eight linebackers because we were trying to decide on a couple of guys, so we were deep at the position," Rivera said. "That doesn't make it any easier, obviously, because you're losing a very good player, but the position should be OK.
"Dan Connor came in and played the remainder of the game, and he played very well, very physical. He had prepped all week to play. It was a heck of a job."
Beason hasn't missed a game in his four-plus seasons in the NFL, starting all 65. It looked like that streak might end at 64 when he missed all four preseason games with a bone bruise in his left heel, an injury that had previously been diagnosed as tendinitis in his left Achilles.
Beason underwent surgery for the injury on Aug. 22 and returned to practice for the first time this season on Wednesday.
"My understanding is that it's on the upper part of the Achilles, away from the foot," Rivera said. "I don't think it's related to what was done. I think it's just an incident that happened.
"He felt great coming into it (the Arizona game)."
All but 12 of Beason's 65 starts have come in the middle. Before Connor's injury last year, Beason started eight games at weakside linebacker in place of Thomas Davis, who missed the entire season with his second major knee injury in less than a year.
Even with all the bouncing around, Beason still led the Panthers with 162 tackles.
"I'm here for him every step of the way, if he needs any advice or anything – even if he needs me to come over and help him move around a little bit," said Davis, who played in his first regular season game in 22 months Sunday and led the team with seven tackles. "I'm there for him. I know that injuries are tough things to deal with, so us as his family are going to be there for him.
"He's played great football for us for a long time, but this was our first game of the season, so we can't sit there and dwell on it and get down. We've got a lot of football left to be played, and we don't want to end up with the same results as last year with a 2-14 season."
Beason's injury, along with the release of offensive lineman Max Jean-Gilles on Sunday, gives the Panthers two open roster spots. Before Beason's injury, Rivera said the Panthers were looking at defensive tackles and offensive linemen to fill the roster spot previously occupied by Jean-Gilles.