The 33-year-old Glenn missed all four preseason games after arthroscopic surgery on Aug. 1 to remove a cyst from the back of his right kneecap. The latest injury came two days ago in practice, coach Wade Phillips said Friday.
"Unfortunately, he had another injury that was not related to the original injury," Phillips said.
The team's Web site said Glenn could be out at least two games, but Phillips said his status beyond Sunday wasn't known. Players were to be available later Friday.
Glenn, entering his 12th season, caught 70 passes for 1,047 yards and six touchdowns last year and gave the Cowboys a deep threat that helped Terrell Owens lead the NFL with 13 touchdowns.
"It's a blow not to have him for this ball game, but there are no excuses," Phillips said. "We're not crybabies. No crying in football."
Patrick Crayton, who has 1,019 yards and seven touchdowns in three seasons, will move into Glenn's No. 2 role behind Owens. Sam Hurd will be the third receiver.
"Patrick Crayton is very dependable," Phillips said. "He's a very heady player. He always finds a way to get open."
Phillips said cornerback Terrence Newman (foot) and backup linebacker Kevin Burnett (ankle) would be game-time decisions.
Outside linebacker Greg Ellis, who's trying to come back from a torn Achilles' tendon, isn't expected to play. If he doesn't, first-round pick Anthony Spencer will start in his place.
Copyright 2007 by The Associated Press. All Rights Reserved.