Dallas defensive end Anthony Spencer will have season-ending surgery on his left knee and may have played his last game for the Cowboys.

Spencer's agent, Jordan Woy, says doctors have a "good idea" what type of surgery but were still considering options. Cowboys owner Jerry Jones spoke earlier on his radio show, saying Spencer was likely to have microfracture surgery.

The 29-year-old Spencer is on a one-year contract with the franchise tag for the second straight season, so he will be a free agent when he's healthy again. He's making $10.6 million US this season.

Spencer originally injured the knee in off-season workouts and aggravated it during a conditioning test the day before training camp. He had arthroscopic surgery July 25 and missed the preseason and the opener against the Giants.

Last year's leading tackler for the Cowboys returned and played more than half the game in Week 2 against Kansas City before he was sidelined again.

"Here's a case of a guy, you almost have to tie him up to get him off the field," Jones said on his radio show. "He was so diligent in his rehab. The individual that I have the most empathy for is Spencer because of the type of person he is."

Microfracture surgery is a procedure to repair cartilage that provides cushion for bones in knee joints. The recovery time is usually at least four months but can be career-threatening for pro athletes.

Spencer, who had career highs last year with 106 tackles and 11 sacks, has described his injury as a bone bruise.

He had just two days of limited participation in practice before playing 34 snaps against the Chiefs. Going into the game, he didn't think he would play more than a dozen or so, but he based that more on conditioning than the status of his knee.

"It didn't seem like it was bothering him at the time," coach Jason Garrett said Monday. "You can't go back eight days ago and say, 'Hey let's have him make 16 plays instead of 30.' We thought we were doing the right thing by him and our football team."

Journeyman George Selvie, who signed several days into camp after it was determined Spencer needed the first surgery, has been a strong replacement and complement to standout end DeMarcus Ware. Selvie has two sacks and five quarterback pressures.