The Chiefs placed Thornton (ankle) on injured reserve Tuesday.
The transaction frees up a spot on the 53-man roster for linebacker Cam Jones, who was signed off the practice squad. After dislocating his left ankle in the Chiefs' Oct. 4 win over the Raiders and requiring surgery, Thornton is facing an estimated recovery timeline of 3-to-4 months, which means that he'll likely be sidelined until at least Week 17 or 18 in a best-case scenario. While Thornton is out, the Chiefs are expected to lean on Jalen Royals and Cyrus Allen to handle more reps in three-receiver sets alongside starters Rashee Rice (hamstring) and Xavier Worthy.