Despite being listed as doubtful, Jennings wants to play and it "sounds like 50-50 at this point," one source told ESPN NFL Insider Adam Schefter on Wednesday.
Coach Mike McCarthy left open the possibility that Jennings could be cleared for at least part of Thursday's game, although Jennings hasn't practiced at all this week.
Jennings worked with athletic trainers Wednesday, and McCarthy said he did not have feedback from that workout at the time he addressed reporters.
Jennings was hurt late in Sunday's loss to the San Francisco 49ers. He had five catches for 34 yards before the injury.
While Jennings can't be replaced, the Packers at least would be in position to credibly use their three- and four-receiver packages without him. Veteran Donald Driver is available to step into the rotation after sitting all but the three plays Jennings missed in last Sunday's 30-22 loss.
An increase in playing time would be welcome news for the 37-year-old Driver, who told reporters Tuesday he was disappointed by his lack of activity in the opener.
"I didn't go into that game thinking I wasn't going to play," Driver said, according to the Green Bay Press Gazette. "The way it came out, I didn't. It sucks, but that's the way it goes."
Jennings also missed time in the preseason because of a concussion. The 2012 season is pivotal for Jennings, whose contract is up at the end of the season.
And although it's only Week 2, history says the Thursday night game at Lambeau Field might be pivotal to the Packers' playoff hopes. According to ESPN Stats & Information, only two teams in the Super Bowl era (since 1966) have started 0-2 -- with both losses coming at home -- and still made the playoffs: the 2003 Eagles and the 1987 Colts. In addition, a Packers loss would mark just the third time in this era that the franchise would have opened a season with consecutive losses at home (1988, 2006).
Information from ESPN.com NFC North blogger Kevin Seifert and The Associated Press was used in this report.