Defensive end Anthony Spencer had targeted Sept. 4 as the date of his return. That was Wednesday, four days before the Cowboys' season opener against the Giants.
But Spencer had a "minor setback" over the weekend when he had swelling in his surgically repaired left knee.
"It feels better today," Spencer said Thursday. "I ran on it. I did some conditioning and stuff. We’ll see how it feels in the morning."
Spencer isn't ruling himself out, calling playing a "possibility", but he doesn't sound optimistic for Week 1. He had a similar scope on his right knee in late August 2008 and missed one regular-season game.
"I wanted to play in this game, so I expected to do some stuff on Wednesday, and I wasn’t able to do that," Spencer said. "It’s not really where I wanted to be at right now.
"...It’s really hard for me, because I love being out there and stuff like that, but at the same time I just got to listen to my body and do what it tells me to do.
Spencer, who has missed six games in his career, including two last year with a shoulder injury, hasn't practiced since undergoing surgery July 25.
The Cowboys already are missing starting defensive tackle Jay Ratliff, who is out at least six games while rehabbing a groin injury. Nick Hayden replaces Ratliff in the starting lineup.
George Selvie would start at left end in place of Spencer. The Cowboys traded for two other defensive ends this week, getting Edgar Jones and Caesar Rayford for depth purposes.
The Cowboys are not expecting running back Lance Dunbar (foot) or safety Danny McCray (hamstring) to play Sunday. Both were on the side doing rehab during practice Thursday.
-- Charean Williams