"I won't know until I guess on Wednesday (when the game plan comes out)," third-year cornerback Sam Shields said Monday. "Right now, I don't know anything. We're just doing a lot of moving around. Hey, you've got to go with it."
This much is set: Veteran Charles Woodson will play safety in the team's base defense and work in the slot or roam around in the nickel and dime defenses. Cornerback Tramon Williams will match up each week with the opposing team's best receiver. And third-year safety Morgan Burnett remains a starter.
But the questions that were at issue throughout training camp apparently remain: Who'll start opposite Williams at the other cornerback spot in the base defense? Which of the team's young safeties will come in for Woodson in the nickel and dime packages? And who'll serve as the sixth defensive back in the dime?
In last Thursday's preseason finale against Kansas City, veteran Jarrett Bush was the No. 2 cornerback, rookie fourth-round pick Jerron McMillian entered at safety in sub packages, and Shields was the dime cornerback. But M.D. Jennings is also an option at safety, Shields could still get the nod over Bush with the starters, and cornerback Davon House hasn't given up hope of playing against the 49ers despite a shoulder injury that has sidelined him since Aug. 9.
Every year, coach Mike McCarthy tries to keep as much of his Week 1 personnel under wraps as he can in hopes of keeping the opponent guessing. In addition to the unscouted looks the 49ers will not have seen on film before Sunday, the coach doesn't want to tip his hand on which players he'll use.
"We're going to have a primary way, a secondary way, different combinations of things based on scheme, and those are the types of things we obviously want our opponent to see on Sunday, not in Wednesday in the paper," McCarthy said. "We're working through it."
The secondary is a primary concern for the Packers after allowing an astronomical 4,924 yards passing last season - the most in NFL history. Although a poor pass rush was a factor in the secondary's struggles - the team's 29 sacks ranked 27th, and no team had a worse sack percentage (sacks per drop back) than the Packers' 4.28 percent - the group knows it must play significantly better this season.
"We know that wasn't us. You can look at the tape from the previous years and look at the one last year, and it just wasn't the same. That just wasn't us," said Williams, who injured his shoulder in the opener last year and essentially played with one arm the rest of the season. "We know that, and that's why we came into training camp refocused, ready to go. We put a lot of good things on film this preseason, and hopefully they carry over.
"I think (the uncertainty) is good. Competition is good. Whoever plays well, that's who's going to get the nod. So it's a good situation."
After struggling early in camp, Shields finished strong with interceptions in the final two preseason games and looking like a more willing and able tackler than he did last season, when he lost his grip on the No. 3 cornerback spot.
Then again, House might have lessened some of the uncertainty had he not dislocated a shoulder in the preseason opener at San Diego. He did not practice Monday and will need time to shake off the rust of sitting out for the past three weeks.
"I'm not going to be able to just go out there and play. It's going to take me a day or two to get my feet back, to get the feel of routes again," House said. "The playbook's there still, which is the most important part, but everything else is probably going to take a day or two to get back."
Whoever lines up at safety alongside Burnett will be inexperienced. McMillian is a rookie, Jennings played just 10 snaps on defense as a rookie last year, and Sean Richardson, the fourth safety, made the team as an undrafted free agent in camp. In all, the Packers kept 11 defensive backs on the 53-man roster, with only Woodson (entering his 15th NFL season), Bush (seventh) and Williams (sixth) having more than two years of experience entering this year.
"Playing young players is something we've done over the last seven years. That will be no different this year," McCarthy said. "It's a process that everyone has to go through. We feel we've prepared our guys through training camp and it's our job as coaches not to ask players, young or old, to do things that they're probably not ready to do on Sunday."
Despite the mixing and matching, Burnett believes the group will be on the same page, regardless of who's out there against the 49ers.
"We have a close group between the corners and safeties, we have a tight bond amongst each other," Burnett said. "Everyone's going to be prepared and ready. Throughout the whole training camp, there's never been a set group, and it's still not a set group. Whenever your number is called, you have to get out there, understand your job and get the job done."