The Panthers placed Thielen (hamstring) on injured reserve Tuesday, Darin Gantt of the team's official site reports.
Thielen sustained a hamstring injury while hauling in a 31-yard touchdown reception in Sunday's 36-22 win over the Raiders and will miss at least the next four games. Carolina signed wideout Jalen Coker from the practice squad to replace Thielen on the 53-man roster, but second-year player Jonathan Mingo and rookie Xavier Legette will be first in line to see added reps behind No. 1 receiver Diontae Johnson while Thielen is on the mend.