Rodgers took the field for pregame warm-ups wearing a sizable brace on his knee.
"He has a pretty unusual injury that would keep most people out awhile," one source told ESPN.
Rodgers was told this week that his injury could take up to a couple of months to heal, according to another source. The star quarterback does not have any ligament damage, according to the source, who said the injury is more of a "compression injury from blunt force while bent."
All week long, players on both the Packers and Vikings have operated as if Rodgers would play.
"He shouldn't have played last week and shouldn't play now, but he likely will," one source said. "There will certainly be a short leash, like there was last week, but we saw what happened."
Wide receiver Davante Adams is also active after being listed as questionable with a shoulder injury.
Rodgers practiced Saturday for the first time since he sprained the knee in Green Bay's thrilling season-opening victory over the Chicago Bears. Rodgers, who threw three second-half touchdowns against Chicago, did not practice Wednesday or Thursday -- the Packers' two longest on-field sessions of the week -- and was listed as questionable Friday.
Unlike most teams, the Packers don't practice on Fridays but instead hold a light on-field session on Saturdays before a Sunday game. Packers coach Mike McCarthy said Friday that he would have no problem playing Rodgers even if he did not practice at all this week.
The Packers will have three quarterbacks available for Sunday's game, with DeShone Kizer and Tim Boyle both being listed as active against the Vikings. Last week, wide receiver Randall Cobb would have been used as the emergency quarterback if both Rodgers and Kizer would have been unable to play.
ESPN's Rob Demovsky contributed to this report.