Spencer originally injured the knee in offseason 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 had career highs last year with 106 tackles and 11 sacks.
Lions WR Burleson breaks arm
Detroit Lions receiver Nate Burleson broke his arm in a single-car accident early Tuesday after he reached over to keep two pizza boxes from falling off the front passenger seat, authorities said. Coach Jim Schwartz stopped short of writing off the rest of Burleson's season, but surgery is scheduled for Wednesday.
"It's not an emergency surgery," Schwartz said. "Nate'll be back at some point, and when he will, he will be a big contributor again to our team."
Burleson's car hit a center median wall on a highway in suburban Detroit and he was taken to a hospital. Michigan State Police Lt. Mike Shaw said there were no indicators of alcohol on the scene or on Burleson's person after the crash at 2:25 a.m.
Burleson has a team-high 19 catches 10 for first downs and his 239 yards receiving is second to Calvin Johnson on the Lions.
Around the league
Colts • Indianapolis waived running back Kerwynn Williams, a seventh-round pick out of Utah State, who was on the practice squad until he was promoted to the active roster when Vick Ballard went down with a season-ending knee injury.
Cardinals • Arizona signed linebacker Vic So'oto to shore up a position severely depleted by injury. The former BYU player was with Washington in the preseason but was released in that team's final roster cut on Aug. 31. He has played in 12 NFL games in his career with Washington, Oakland and Green Bay.
Week 4 schedule
San Francisco at St. Louis, 6:25 p.m., NFL
N.Y. Giants at Kansas City, 11 a.m.
Seattle at Houston, 11 a.m., Ch. 13
Baltimore at Buffalo, 11 a.m.
Arizona at Tampa Bay, 11 a.m.
Indianapolis at Jacksonville, 11 a.m.
Cincinnati at Cleveland, 11 a.m.
Chicago at Detroit, 11 a.m.
Pittsburgh vs. Minnesota at London, 11 a.m., Ch. 2
N.Y. Jets at Tennessee, 2:05 p.m.
Washington at Oakland, 2:25 p.m.
Dallas at San Diego, 2:25 p.m.
Philadelphia at Denver, 2:25 p.m., Ch. 13
New England at Atlanta, 6:30 p.m., Ch. 5
Open: Carolina, Green Bay
Miami at New Orleans, 6:40 p.m., ESPN