The victory also gives the Packers a much-needed boost on the road, in poor conditions against a playofff caliber team.
The 49ers had took the driver's seat with four minutes remaining in the game. The Packers had been stopped in the red zone and had to settle for a Ryan Longwell field goal which kept the Niners within a score.
San Francisco used a classic West Coast offense to march downfield, aided by a defensive holding call.
But on their final set of downs, the previously precise 49ers couldn't solve the Packer D.
Jeff Garcia's fourth down pass fell far short of its target, stopping SF on the 11 with 22 seconds to go and setting off a Packer victory celebration.
"I had confidence in our defense, but man, I was also pretty confident they could score,'' said Favre, who improved to 10-1 against the Niners.
After the victory, Favre fought his way across the field to shake Steve Mariucci's hand in the middle of Candlestick Park. "That one could have gone either way,'' Favre told his former quarterbacks coach.
The Packer party was a happy contrast to 49ers receiver Terrell Owens earlier stunt. After catching a pass and running over Mike McKenzie to a TD, Owens accepted a set of pom-pons from a cheerleader and performed a dance.
The Packers looked like a team gearing up for the post-season, with the usual suspects stepping up with big games.
Ahman Green ran for 90 yards and a touchdown, and Terry Glenn made a couple of big first-down grabs as the Packers shrugged off the miserable conditions to score 17 points in the second half while holding San Francisco scoreless in the fourth quarter. Fullback William Henderson stepped up with five catches for 33 yards, while Driver eclipsed the 1,000-yard mark for the season.
"This game should propel us through the last two games and into the playoffs,'' Green Bay safety Darren Sharper said. "If we didn't believe we're good in big games, this game definitely tells us we can win them.'' Owens caught eight passes for 75 yards and a touchdown -- which he punctuated with a pompom-waving celebration -- but the 49ers again struggled to move the ball. The Packers held them to just 263 yards total offense.
"I've played in a lot of games, but that's one of the best games I've played in,'' Favre said. "Just a well-played game by both teams in some terrible conditions.''
The teams were both stalled at 50 yards passing in the first half, but Favre and the Packers immediately took control after halftime. Favre broke through a conservative game plan to lead a 79-yard drive from the kickoff, with Green scoring on a 9-yard run.
Green Bay did not turn the ball over, despite the terrible conditions, but did manage a takeaway. Garcia threw a pass as he was being tackled -- and it ricocheted off the back of offensive guard Matt Willig to Vonnie Holliday, who lateraled the ball to Na'il Diggs for a long return.
Favre struck again, hitting Driver for a 5-yard TD that put Green Bay up 17-6.