ENGLEWOOD, Colo. — A third injury to the area around his left knee finally finished off Denver Broncos linebacker Danny Trevathan for the 2014 season.

Trevathan suffered a dislocated kneecap in the second half Sunday, ending his return to the lineup after missing the previous eight games with a crack just above the knee. He missed the first three regular-season games because of a tibial impaction fracture just below the knee.

“Danny’s had a rough season as far as knee issues,” Broncos coach John Fox said. “Sometimes setbacks are setups for better things to come. That will be his mindset as he gets ready for surgery and then gets ready for the pretty strenuous rehab involved to come back.”

Exacerbating matters in the short term for the Broncos was the mid-foot sprain suffered by Brandon Marshall, who filled in for Trevathan through most of the regular season to date. Without the two linebackers, the Broncos shifted safety T.J. Ward back to linebacker in the nickel package and used rookie Todd Davis as a weak-side linebacker.

The Broncos’ production from the weak side has been one of the defining characteristics of coordinator Jack Del Rio’s defense, dating to Wesley Woodyard in 2012. But the absence of Trevathan and Marshall will test that trend.