GREEN BAY — While having a top-flight quarterback may be vital to achieving consistent, year-in and year-out NFL success, losing your star signal-caller doesn’t necessarily have to be a death knell for your season — as it turned out to be for the Green Bay Packers.

Just ask the Philadelphia Eagles and Minnesota Vikings, who’ll play in today’s NFC Championship Game at Lincoln Financial Field in Philadelphia. One of them will advance to Super Bowl LII in Minneapolis on Feb. 4 — and will do so without their season-opening starting quarterback.

Case Keenum, a 29-year-old journeyman who started 24 games in five years with two teams (the Houston Texans and St. Louis/Los Angeles Rams), has the Vikings one win away from playing in the Super Bowl on their home field at U.S. Bank Stadium after starter Sam Bradford’s early-season knee injury.

Nick Foles, who turned 29 on Saturday and started 24 games in three years for the Eagles during his first stint in Philadelphia, is back under center after bouncing around to the Rams (2015) and Chiefs (2016) before returning as Carson Wentz’s backup this season. Wentz, an NFL MVP candidate, suffered a torn anterior cruciate ligament in a Dec. 10 game against the Rams. The Eagles were 11-2 and already closing in on the NFC’s No. 1 seed.

According to NFL Research, the game will mark the first time since at least 1970 that two quarterbacks who did not play Week 1 as the team’s starter, will meet in the conference championship.

“I know this is what all of you guys predicted back in the day, a Foles versus Keenum NFC Championship,” Keenum said, joking with reporters at midweek. “So good job to all of you guys who predicted that.”

So how did this happen? How, in a quarterback-driven league, are two backups battling for a trip to the Super Bowl?

De-fense! De-fense!

“I think it says that they are on great teams, quite honestly,” said Eagles coach Doug Pederson, a former backup quarterback who had two stints — 1995 through ’98, and 2001 through ’04 — backing up Brett Favre in Green Bay. “Listen, I’ve said this a lot of times and I’ll say it again: It’s not about one guy. Even (New England Patriots quarterback) Tom Brady has weapons on offense and (a) good defense.”

That is true. The Vikings ended the season ranked No. 1 in the NFL in total defense (275.9 yards allowed per game) and scoring defense (15.8 points allowed per game), and the Eagles finished fourth in both total defense (306.5) and scoring defense (18.4).

By comparison, the Packers’ much-maligned defense finished the 2017 season 26th in scoring defense (24.0) and 22nd in yards allowed (348.9).

So in a year when the team desperately needed help with two-time NFL MVP Aaron Rodgers missing 10 games, the defense couldn’t come through.

“Obviously, when you lose Aaron, you lose a great deal of the offense. But not only that, you don’t take into account what it does (for the defense) when you’re playing ahead, or what it does when you can run certain plays and flip the field,” outside linebacker Clay Matthews said late in the season. “There’s so much more to having a guy like Aaron on the field.

“But you’re right. At the end of the day, it’s not enough. Your success is based on wins and losses in this league, and we just didn’t do enough (on defense).”

According to calculations done by’s Rob Demovsky, the Packers spent 40.77 percent of their 2017 salary-cap space on defensive players, compared to 45 percent by the Eagles and 52.14 percent by the Vikings. But it would be wrong to say the Packers haven’t invested in their defense, considering in their past six drafts starting with 2012, they devoted 20 of 29 picks in the first four rounds to defense (69 percent). But unlike the Vikings and Eagles, who hit on a number of their picks and then augmented them with free agent pickups, the Packers’ success rate has been disappointing.

“The philosophy with (general manager) Rick (Spielman) and myself has always been we build through the draft, and then add guys through the free agency,” Vikings coach Mike Zimmer said. “We added a few guys from free agency when I got here, but we’ve drafted guys (too). … So our scouts have done a good job of identifying the guys, and I think the coaches have done a good job in communicating with those guys with the kind of guys that we need.”

Experience matters

The other significant disparity is who each team had as its backup quarterback — experienced vets versus a developmental youngster.

Whereas Packers backup Brett Hundley came into the season having never started an NFL game and never taken a truly meaningful snap — Rodgers hadn’t missed extended time with an injury since breaking his left collarbone in 2013, while Hundley was still at UCLA — Foles had started 36 regular-season games with the Eagles, Rams and Kansas City Chiefs entering 2017, while Keenum had started 24 games with the Texans and Rams before joining the Vikings.

In four starts for the Eagles, including last week’s NFC divisional victory over Atlanta, Foles has completed 70 of 117 passes (59.8 percent) for 685 yards with five touchdowns and two interceptions with five sacks (83.5 passer rating).

In 15 starts for the Vikings, including last week’s NFC divisional win over New Orleans, Keenum has completed 333 of 500 passes (66.6 percent) for 3,725 yards with 22 touchdowns and eight interceptions with 24 sacks (96.6 passer rating).

Including the Oct. 15 loss to the Vikings, during which Rodgers fractured his right (throwing) collarbone on a tackle by Minnesota linebacker Anthony Barr after a first-quarter pass, Hundley saw extended playing time in 10 games. He started nine of those, in which the Packers went 3-6, with their victories coming over the Cleveland Browns, Tampa Bay Buccaneers and Chicago Bears, who sported a combined 2017 record of 10-38.

He finished the season having completed 192 of 316 passes (60.6 percent) for 1,836 yards with nine touchdowns, 12 interceptions and suffered an astronomical 29 sacks (70.6 passer rating).

A fifth-round pick in 2015, Hundley spent his rookie season as the third-string quarterback behind Rodgers and veteran backup Scott Tolzien before being elevated to the No. 2 job in 2016. When Rodgers went down, McCarthy made it abundantly clear that he saw no need to find a veteran backup to install behind Hundley, saying repeatedly that the quarterback room was “exactly where it needs to be.”

Would a veteran backup have given the Packers a better chance when disaster struck? That’s hard to say. Hundley did play well enough for the Packers to win three games and stay in playoff contention for Rodgers’ return to the lineup on Dec. 10 at Carolina, but Rodgers had to push the medical staff hard to let him play, and if the Packers had won another game or two in his absence, he’d have had more time to heal instead of rushing back for the earliest game in which he could play.

Twice, the Packers were shut out with Hundley as the starter, and 11 of his 12 interceptions came in losses. While it would be unfair to say Keenum and Foles haven’t made many plays — especially to Keenum, whose 61-yard miraculous scoring pass to Stefon Diggs last week saved the Vikings — they have avoided costly turnovers.

“You can definitely appreciate (what they’ve done) as a backup quarterback,” Pederson said. “They just seem to keep sort of defying the odds and stepping up to the challenges each week. That’s what’s exciting and fun to see about these two guys is they’ve just overcome everything and have really, really helped their teams get to this position. And that’s what you want.”

But, Pederson added, “Bottom line, it comes down to who can take care of the football.”

Successful formula

After the season, McCarthy set the lofty goal that the defense needed to be better than the offense in 2018. That would obviously be ideal, as would having his star quarterback avoid injury.

Other than the collarbone injuries in 2013 and 2017, Rodgers has missed only one start due to injury since becoming the starter in 2008, having missed a 2010 game at New England with a concussion. If disaster strikes again, the Packers will need better play from the backup — whether it’s Hundley or someone else next season — and from the defense.

But don’t expect the Packers to alter their formula significantly based on their 2017 failure — and the Eagles’ and Vikings’ success.

“Teams that have great players, you tend to center your team on where your strengths are. That’s what you’re supposed to do,” McCarthy said in a late-season sit-down interview. “So, we built the offense around making the quarterback successful. And we’ve been blessed to have two Hall of Fame quarterbacks. That’s obviously the starting point.

“You look at the way we’ve played without Aaron, that part is fair criticism. But we’re talking about football here — the ultimate team game. Great player, but it’s 11 on 11. I understand how hard it is to win a game, I definitely understand how hard it is to win a Super Bowl. The fact that you’re successful over a long period of a time, that’s a sign of a good program.”