His agent Brian Levy told multiple news agencies Tuesday that Jenkins' torn pectoral muscle will require surgery, making coming back this season impossible.
Jenkins was injured as he grabbed Buccaneers quarterback Brian Griese during a sack attempt early in the fourth quarter. Griese escaped to compete a 17-yard pass.
In the locker room Monday, Jenkins said he was unable to lift his right arm above shoulder level.
"He's going to need surgery, so he's going to have to go on injured reserve," Levy told the Green Bay Press-Gazette. "The timing couldn't be worse. ... It's a big blow, but he'll come back from this stronger."
The Packers made no formal announcement Tuesday about Jenkins' status. General manager Ted Thompson was traveling on a scouting trip and unavailable.
Levy did not immediately return a call from The Associated Press Tuesday night seeking further comment.
Jenkins had started the season as a leader of Green Bay's defensive line. In four games, he had 2½ sacks, 10 quarterback pressures, a forced fumble and 18 tackles.
The Packer defense earlier lost veteran cornerback Al Harris to a lacerated spleen suffered in the loss to Dallas Sept. 21. Harris is expected to miss at least three more games.
Linebacker A.J. Hawk suffered a groin injury Sunday and could miss next Sunday's game against Atlanta.
Safeties Nick Collins (back), Atari Bigby (hamstring) and Aaron Rouse (knee) are all battling injuries, and cornerback Charles Woodson is playing with a broken toe on his right foot that has prevented him from practicing each of the past three weeks.
On offense, starting quarterback Aaron Rodgers has a sprained right shoulder, left tackle Chad Clifton has a hamstring injury and running back Ryan Grant has been nursing a training-camp hamstring injury for the first four weeks of the season.
Copyright 2008 by The Associated Press