The second-year player was hurt when he picked off a pass in the end zone and attempted to run it out in the Packers' win over St. Louis on Oct. 16. Shields never made it out, taking a blindside hit from Rams receiver Brandon Gibson.
The injury left Shields dizzy and stricken with headaches for a few days. He says it was his first concussion at any level of football, and he was busy Friday questioning his position coach about the protocol for what a defensive player should do when he intercepts a pass in the end zone.
"He said, 'Now, if I'm this deep, can I come out of there?'" cornerbacks coach Joe Whitt recounted after practice. "I said, 'You do what you want to do now, but you understand what you're supposed to do.'"
Shields was cleared to practice after the Packers had their bye week. It gave him time to think about the injury.
"Everybody said I should've (gone) down. I should've, but things happen," Shields said earlier this week. "It's a learning process. Next time, I'll go down."
Or will he?
Shields changed his tune somewhat in the locker room Friday after he was asked what he would do the next time he intercepts a pass in the end zone.
"You never know," he said. "We teach in our secondary group is whenever we catch the ball we're looking to pick-six. Every time we get our hands on the ball, we're trying to score. That's our mentality for our secondary on defense."
Green Bay's defensive backs, including Shields, have been under some scrutiny this season. The Packers have allowed an average of nearly 290 passing yards per game, ranking second to last in the NFL.
Giving up big plays has been a sore spot in Green Bay's magnificent season. Opponents have gashed the Packers for 37 plays of at least 20 yards, and 32 of those have come via the pass.
"We're the same secondary that, in my opinion, is the best in the league, but we haven't played that way, and that's on me," Whitt said. "I'm doing a poor job of getting them ready to play. Nothing more than that. If I do my job, they play at a high level. If I don't do my job at a high level, it affects their play. That's basically what it is."
The big chunks of yardage have been mitigated by the Packers' knack for creating turnovers. They are tied for second in the league with 13 interceptions and tied for third with 16 takeaways.
Following a slow start, Shields has been contributing with momentum-changing plays after he made an impact as an undrafted rookie last season with four interceptions, including two in the Packers' NFC championship win at Chicago.
"He looks like he was in the playoffs, where he really realized he's a DB (defensive back) and how he can play," Whitt said. "I'm excited about him."
As the team's frequently used nickel back, Shields has two interceptions this season.
Shields credits his improved play after teams had success throwing on him early in the season to getting back to playing press coverage on receivers.
"I kind of got out of my groove," he said. "I'm usually pressing. I kind of got out of it and started playing off, and that wasn't me. So, I went back to my old ways and pressing. Hey, that's what I'm good at, so why not just keep going with it?"
Whitt took responsibility for how Shields was positioned off the line of scrimmage in the team's first two games, calling it a miscommunication.
"I've got to get that stuff cleared up quicker," Whitt said. "But once he realized what we wanted from that situation, he's been playing really, really high-level football."
And the coaches are hopeful Shields will make the right decision the next time he comes up with the football.
"Sam's an aggressive thinker when he gets the ball in his hands," defensive coordinator Dom Capers said. "He knows he's got that speed, and no matter where he is, he think he's going to take it and score. That's one of the things about being a young guy, you get clobbered a couple of times like that, your judgment improves, I think."
Shields returned his first interception this season a career-long 60 yards out of the end zone against Denver on Oct. 2.
"It's very easy to sit there after the fact and question a player's decision in the heat of battle, especially when he makes a decision a couple weeks before and comes out of the end zone and makes a big play," coach Mike McCarthy said. "You can't have it both ways. We're either going to catch it and kneel down, or catch it and try to come out and be smart. It's a learning experience for Sam. I feel strongly that he's learned from it."