The Dallas Cowboys placed starting defensive end Anthony Spencer on season-ending injured reserve and picked up cornerback Chris Greenwood from the Detroit Lions' practice squad on Wednesday.
Spencer faces surgery on his left knee, said his agent, Jordon Woy. It is the same knee that underwent surgery two months ago.
The 29-year-old Spencer missed all of the preseason after the first surgical procedure before he returned to play in the opener against the New York Giants. He injured the knee again during a Week 2 game against the Kansas City Chiefs.
George Selvie replaced Spencer and has two sacks and seven tackles in three games.
Greenwood was selected in the fifth round of the 2013 NFL Draft by the Lions. He sat out his rookie season with a torn abdominal muscle.