An exam confirmed Denver Broncos center Dan Koppen tore the anterior cruciate ligament in his left knee on Sunday, according to Jeff Legwold of the Denver Post. Koppen was carted off the field after he heard a pop in the knee.
With Koppen lost for the season, the Broncos have a significant hole to fill at the center position. Koppen started 12 games last year as a fill-in for J.D. Walton, who suffered a major ankle injury in September. Walton had another surgical procedure done on the ankle in June, leaving his availability for the 2013 season in doubt. At minimum, it appears he won't be able to play until late October or early November, barring setbacks.
That's why Denver signed Koppen last month; the 10-year veteran has started more than 130 games in his career and would have served as a useful stopgap, just as he did a year ago. Manny Ramirez, normally a guard, is handling the snapping duties for now.