Englewood, CO (Sports Network) - The Denver Broncos placed center Dan Koppen on injured reserve Tuesday.
Koppen suffered a torn anterior cruciate ligament in his left knee during Sunday's practice.
The 33-year-old Koppen started 12 regular-season games and one playoff contest for the Broncos last year.
Koppen took over for J.D. Walton last season after the latter fractured his ankle against the Oakland Raiders in Week 4. Walton underwent further surgery on his ankle in June and is still expected to miss a significant portion of the upcoming season.
The 6-foot-2, 300-pound Koppen played for the Patriots from 2003-2011 before joining the Broncos.