The Colts placed Buckner (neck) on injured reserve Saturday.
Head coach Shane Steichen said on Friday that Buckner, who had just returned from a stint on IR in Week 16, aggravated his neck injury and will undergo a procedure in Week 18, per Amanda Foster of the team's official site. He initially injured his neck in Week 9. The veteran defensive tackle will be eligible to return from IR in late January if the Colts advance far enough into the playoffs, though it's unclear whether his recovery timetable would allow for that, plus the team has only a very slim chance of sneaking into the postseason.