Shields joined his teammates on the practice field Monday as the players returned from a six-day hiatus for the bye week. Shields had been sidelined since he sustained a concussion in the third quarter of Green Bay's win over the St. Louis Rams on Oct. 16 at Lambeau Field.
The injury occurred when Shields intercepted a pass from the Rams' Sam Bradford in the end zone and then tried to run it out, only to get pasted by St. Louis receiver Brandon Gibson while running across the end zone.
"Everybody said I should've went down (after the interception)," Shields said. "I should've, but things happen. I'm ready to go.
"It's a learning process," he added. "Next time, I'll go down. In my mind, I wasn't thinking about all that. I was thinking about scoring. But, making the right decision is going down and letting the offense go and score."
The team's medical staff cleared Shields to resume football activities before the players were excused for the bye week following meetings Oct. 24, a day after Green Bay beat the Minnesota Vikings to improve its NFL-best record to 7-0.
Barring a setback this week in practice, Shields is expected to be OK to play Sunday, when the Packers will play at the San Diego Chargers.
Green: Could have been worse
In the wake of a season-ending knee injury sustained by rookie Alex Green in the Oct. 23 win at the Vikings, the Packers replenished the depth at running back by promoting undrafted rookie Brandon Saine from the practice squad, taking the spot of Green, who went on injured reserve.
"Brandon has earned this opportunity," McCarthy said. "I'm excited for him. He'll have an opportunity to compete for a spot on the (game-day) 46 (-man roster) this weekend against San Diego. He's done a tremendous job throughout his time here. At training camp, he was impressive, a very nice surprise for me, personally."
Green confirmed Monday he sustained a torn ACL in his left knee. He was injured when he collided with teammate Randall Cobb at the end of a kickoff return by Cobb in the first quarter of the last game.
"They thought it was the MCL and ACL first, but I guess it's just the ACL. If there is any good news, it'd be that, that it's not both," Green said. "It's still early, it hasn't been a full week yet (since the diagnosis), but I can already tell that mentally it's going to be a challenge to just stay in-tune with everything and not get too down and try to look at things with a positive outlook."
Surgery for Green has been delayed until swelling in the knee subsides.
Saine had 19 carries for 51 yards for the Packers in the preseason, ranking third on the team, and led Green Bay's running backs with six catches for 36 yards.
"It still hasn't really hit me that I'm going to get this opportunity," Saine said. "I think (special teams) is a good place for me to start. I think I can fill Alex's role where he was - he was on all of the special teams. I think that's definitely a good place for me."
-- Left tackle Chad Clifton didn't practice. Clifton has missed the last two games because of a partial tear to his right hamstring. Clifton's status for this week, including Sunday's game, won't be determined until Wednesday at the earliest. Marshall Newhouse would remain the starter if Clifton can't go.
-- Outside linebacker Frank Zombo returned to practice and participated on a full-time basis. "I wasn't supposed to, but I jumped in there and I told them I was doing awesome, so the trainers were like, ‘Well, if he feels good …' So, I did everything." Zombo missed the last game before the bye because of a hyperextended knee. He has appeared in only one game this season, missing the first five games because of a broken shoulder blade.
-- Defensive end Mike Neal has yet to be cleared by the medical staff for a return to the field. The second-year player and projected opening-day starter hasn't played a down in 2011 after he suffered cartilage damage in his left knee during training camp and then underwent surgery Sept. 13. It's unclear whether Neal will play this season.
-- Nine teams are averaging at least 25 points per game. If that holds up, that would tie the league record set in 2008. With the Saints laying an egg against St. Louis, Green Bay is averaging a NFL-high 32.9 points per game.