"He went and saw Dr. (Robert) Anderson yesterday, and there was a lot of concern," head coach Ron Rivera said. "Today, everything was confirmed.
"He is going to be lost for the season… It's unfortunate. He was having a terrific year."
The injury occurred sometime late in the first half, but Kalil – a three-time Pro Bowler – finished the game.
"I think (the injury happened) just before the half," Rivera said. "He got some treatment, they re-taped his foot and brought him back out there and he finished the game. The assumption we were (going) with was that he was going to be fine."
The surgery is expected to be done "sometime next week."
Rivera said the long-term prognosis for Kalil after he completes his rehab "should be very good," but that hasn't made the devastating news any easier to take.
"He's struggling with it," Rivera said. "He wants to be out there with his guys and fighting for us. It's a tough pill for him to swallow right now, but he'll bounce back."
"Hangartner is our initial (replacement)," Rivera said. "We'll work him there.
It's near-impossible to replace a three-time Pro Bowl center midseason, but the Panthers are fortunate to have an experienced backup and are very fortunate that he's healthy. Hangartner had started 20 consecutive games at right guard for the Panthers before missing last Sunday's game against Seattle with a knee injury, but he is recovering nicely.
To boot, 47 of his 55 starts before he returned to the Panthers last season had been at center.
"I'm feeling good, feeling a lot better," Hangartner said Wednesday. "I've come a long way in the last week-and-a-half. I fully anticipate being back out there on the practice field next week and playing in the game."
Beyond Kalil's productivity, the Panthers must proceed without one of the locker room's outspoken leaders.
"He is most certainly one of the emotional leaders, and it's hard to replace those kind of guys," Rivera said. "The truth of the matter is it's time for us as a team to step up. This is another one of those things that's going to try us."