According to the team's official website, Panthers head athletic trainer Ryan Vermillion said Kalil will be "evaluated on a weekly basis," putting his status for Week 1 of the regular season in question.
Kalil, 29, was a stalwart for the Minnesota Vikings at left tackle across five years with the organization after it used the No. 4 overall pick on him in 2012. He started 66 straight games to begin his career. The Panthers signed him away from Minnesota with a five-year, $55.5 million contract last March.
His extended stretch of durability came to a close early in the 2016 season, though. Minnesota placed him on injured reserve in September with a torn labrum in his right hip. He missed the final 14 games of the campaign as part of the first absence of his career.
He bounced back to play all 16 during his debut season in Carolina.
If the latest setback forces him to miss additional action, the Panthers will likely turn to second-year man Taylor Moton to fill in at left tackle with Jeremiah Sirles replacing the injured Daryl Williams at right tackle.
All told, while Kalil has never consistently established himself as one of the league's top tackles, the Panthers bet big on him helping improve their line. Carolina will hope he's able to get back to full strength and return to his previously durable ways so he can anchor the front five.