GREEN BAY, Wis. -- We've learned quite a bit more in the past five months about what coach Mike McCarthy considers essential positions.

In the world according to the Green Bay Packers coach, you can live without a Pro Bowl left guard (see Josh Sitton's release back in September). But lose key members of the secondary and have others fail to live up to expectations and it can be nearly impossible to overcome. The same goes for pass-rushers.

And in many ways, that tells the story of the Packers' season.

The Packers had a porous secondary this season -- ranking almost last in passing yards allowed. Bill Streicher/USA TODAY Sports

The offense functioned just fine after the Packers dumped Sitton on the day of final roster cuts following the preseason. But the defense never really came up with a way to play with an inexperienced group of cornerbacks that were forced into bigger roles after veteran Sam Shields was lost to a season-ending -- and possibly career-ending -- concussion in the regular-season opener. Nor did it find a consistent reliable pass rush with or without Clay Matthews, who battled hamstring and shoulder injuries most of the season.

McCarthy essentially conceded that it was an issue with personnel -- not scheme or playcalling -- that doomed the defense, and it's why he apparently doesn't plan to fire defensive coordinator Dom Capers, who received an endorsement during McCarthy's season wrap-up session with reporters Thursday when McCarthy called Capers "an outstanding football coach; that doesn't change."

"You have two positions on defense that I consider primary positions, that's pass-rushers and corners," McCarthy said. "Because if you don't have either, you have to change the way you play schematically. No different on offense. If you don't have the left tackle or quarterback, that dramatically changes the way you have to play."

So where does that leave McCarthy and Capers?

Perhaps that's a better question for general manager Ted Thompson, who will have to determine whether the three second-year cornerbacks -- Damarious Randall, Quinten Rollins and LaDarius Gunter -- can be their nucleus again but produce different results. The Packers ranked 31st out of the 32 teams in passing yards allowed last season.

Even though Shields said last week that he wants to keep playing despite recurring headaches, McCarthy confirmed Thursday that the veteran cornerback still hasn't been cleared from the concussion protocol more than four months after his last one. Given that Shields has only been available for two of the past 23 games, including playoffs, it's unlikely the Packers will count on him. In fact, they'll probably release him in order to save $9 million off their salary cap.

Gunter, while reliable, is limited athletically and even though he had success this season, he was overmatched as a shut-down corner, which was evident in the NFC title game against Julio Jones.

Randall (a 2015 first-round pick) and Rollins (a 2015 second-round pick) were injured throughout the season and failed to make a big enough jump from their rookie seasons.

"I think when you look at the young men that you just referred to, they did a lot of good things in their first year," McCarthy said. "We have a long history here in the last 11 years of first-year players making a big jump in their second year, so you have to factor that into those types of decisions. And those guys, both Randall and 'Q' Rollins, had multiple injuries to deal with, too. It was a tough go at the cornerback position. I thought Joe Whitt did a tremendous job getting those guys ready. We just really never had any consistency as far as who we were playing with in multiple weeks. Obviously, Gunter gave us the most consistent play in his time, and he deserves a lot of credit for that."

Still, McCarthy wouldn't commit to anyone as a future starter.

"I think they're both going to be really good players for us," McCarthy said.

"Both Q and Damarious will be working out together out there in California, so these guys already have their workout plan set, they're starting in a week or week and a half. So those are the things we're really focused on. I think both those guys will definitely grow for their experience this year, because they both had a lot of adversity that they had to deal with."

There may be just as many questions about the Packers' pass rush considering their top-two sack leaders -- Nick Perry (11 sacks) and Julius Peppers (7.5) -- have come to the end of their contracts, and Matthews (5 sacks) seems to have better luck staying healthy as an inside linebacker.

"He missed games with the hamstring and, obviously, I thought he fought through the shoulder injury, which as we know was a big injury," McCarthy said. "Once again, this outside linebacker/inside linebacker deal, I don't know why we have to keep trying to put him in a place. He moves around. If you watch the games, he doesn't always line up in one spot. I think that's very important for us to continue to do that. Frankly, if he doesn't have the injuries, you would have seen a lot more of it this year. He's a playmaker."