The Panthers designated Kalil as a post-June 1 release, Jourdan Rodrigue of the Charlotte Observer reports, saving them $7.25 million in salary cap room.
Kalil went on injured reserve Sept. 2 with a right knee injury and missed the entire season. Chris Clark started at left tackle most of last season, but the Panthers could have Williams and Taylor Moton as their starting tackles next season. Williams played only one game last season because of a knee injury.
Kalil, 29, also missed most of 2016 after tearing the labrum in his right hip. He played only two games for the Vikings that season but started all 16 games at left tackle for the Panthers in 2017.
Kalil has made one Pro Bowl and that came in his rookie season of 2012 after the Vikings made him a first-round pick.