Before we discuss Saturday night’s Battle by the Bay, read this excellent Milwaukee Journal Sentinel story about the depth and breadth of Packer Nation:

When the Green Bay Packers meet the San Francisco 49ers in the NFL playoffs Saturday night, the hopes and dreams of a nation will be riding on the outcome.

Packer Nation.

On Guernsey Island, off the coast of Normandy in the English Channel, Paul De La Mare will cheer for the team he adopted in the 1980s, when he discovered American football on the Armed Forces Radio Network.

In Rome, orthopedic surgeon Stefano Ruzzini, 61, will be as emotionally involved as any Packers fan in Appleton or Little Chute. Why? Ruzzini lived in Wauwatosa as an AFS student in 1967-’68, the tail end of the Glory Years in Green Bay. He’s been a die-hard ever since.

In Montreal, Hugues Bertrand, who teaches a high school leadership class and refers often to the example of Vince Lombardi – the iconic coach he read about as a teenager – will be glued to the television.

And, of course, in living rooms across Wisconsin, thousands of fans will jump out of their chairs on one play and sink into them on the next.

The Packers are not the only professional sports franchise with passionate fans scattered across the globe.

But there is something different about Packer Nation.

It’s hard to define. It’s difficult to articulate. It’s something you know to be true but can’t quite explain.

Take it on faith. Take it from the fans themselves.

The Journal Sentinel recently asked for submissions from fans describing how and why they became Packers fans. The response was over whelming: 272 emails poured in, along with four handwritten letters, from 32 states and nearly one dozen countries. …

In many cases, kids cheering for Aaron Rodgers and Clay Matthews today have parents who cheered for Lynn Dickey and James Lofton in the 1980s, grandparents who cheered for Paul Hornung and Ray Nitschke in the ’60s and great-grandparents who cheered for Don Hutson and Tony Canadeo in the ’40s. …

Greg Steffen grew up in Iowa and watched the Ice Bowl with his brother, a Cowboys fan. Steffen did not have a favorite NFL team and decided he’d pledge his loyalty to whichever team won.

“It all came down to that final gutsy call with 16 seconds left,” Steffen wrote. “Starr snuck the ball across the goal line for the victory. I still remember my brother collapsing in front of the TV. And I had a favorite NFL team, the Green Bay Packers, for the rest of my life.

“Not lost on me over the years is the fact that I came one great Jerry Kramer seal block away from being a Cowboys fan for life. Yikes!”

Kelly Mayo of West Bend watched the Ice Bowl with his family and the experience of seeing his tough father – “an Irish cop right out of central casting” – shed tears when Starr scored has stayed with him his entire life.

“I had never seen this giant of a man cry and I have never seen it since,” Mayo wrote. “Not when his mother died, not when his sons went to Vietnam or more importantly when they came back, not ever before or since.

“But watching my Dad cry on that glacial Sunday, I became a rabid, dyed-in-the-wool, lifelong Packer fan! I began to understand what they meant to my Dad – hope, a collective that was bigger than ‘one,’ pride, belonging, something to help escape the mundane and perhaps most essential something human and personal.

“And that is what the Green Bay Packers exemplify to me to this day.”

In 1966, 8-year-old David Welsh of Lexington, Ky., wrote a school report on Starr, an athlete his pastor-father admired and respected. He got an A-plus grade (“Thank you, Mrs. Collins”) and decided to mail a copy of the report to Starr.

“I don’t know if he ever saw it, but a few weeks later I received an autographed picture from the future Hall of Fame quarterback,” Welsh wrote. “That day, standing at the mailbox in a foot of snow, I became a Packer fan for life.”

Never in my life have I ever cried over the result of a sporting event, including the three Super Bowls I remember watching. (I probably watched Super Bowls I and II too, but given that I was 1½ and 2½, respectively, I don’t remember the games.) I have gotten murderously angry at the results of certain Packer games, though not of Super Bowl XXXIII. My wife and I are Packer shareholders, and our kids are on the season ticket waiting list (five digits in each), so we have a personal commitment, as opposed to fans of lesser NFL teams.

If you were asked to identify the Packers’ biggest rival that is not in the NFC North, you probably would answer one of three choices — Dallas, the New York Giants, or San Francisco.

The Packers–Cowboys rivalry dates back to the Packers’ first two Super Bowl appearances, both of which went through Dallas, and was heightened by the three consecutive seasons in the ’90s where the Packers’ playoff trips ended in Dallas. The Packers–Giants rivalry is one of the NFL’s oldest, stoked by the hiring of Giants offensive coordinator Vince Lombardi to be the Packers’ coach (resulting in consecutive NFL championships), and recently amped by the Giants’ ending the Packers’  playoff trips in two of the past five seasons.

However, neither the Cowboys nor the Giants are in the 2012 NFL playoffs. The 49ers are.

Even though the 49ers and Packers have been in the same league since the 49ers moved in from the  late All-American Football Conference, the real rivalry dates back to when Packers general manager Ron Wolf hired 49ers offensive coordinator Mike Holmgren to be the Packers’ coach. Before that, the Packers and 49ers were never good at the same time, though in many seasons they were bad at the same time.

Holmgren, a San Francisco native, brought with him not just the 49ers offense as designed by Bill Walsh, in which passing replaced running as a means of ball control. (Which is an interesting story in itself. Walsh was an assistant coach Paul Brown, one of football’s greatest innovators, with the Cincinnati Bengals. which one particular season saw their cannon-armed quarterback get injured. The quarterback’s backup was decidedly not cannon-armed, but lacking much of a running attack, Walsh had to make do with what he had, and it worked, with the Bengals throwing short passes to control the ball through the air.)

Holmgren also brought the absolute insistence of doing things the right way, even off the field. (I’m not sure where I read it, but one Packer book tells the story of Holmgren’s upbraiding the Packers’ traveling staff because of some sort of hotel issue. Whatever the issue was, it never happened again.)

Brett Favre’s autobiography, Favre, tells the story of the Packers’ 27–17 upset in San Francisco in the 1995 playoffs. Packer defensive end Reggie White had a swear jar in which anyone who swore was supposed to put money in the jar. So when Holmgren began the first meeting the beginning of the week before the 49ers game, he announced, “We’re going to beat these fuckers,” and put in a $100 bill. And then to be sure everyone heard him, he said, “We’re going to beat these fuckers!” and added another $100 bill. Favre wrote that that got everyone’s attention.

That win started a run of four consecutive Packers–49ers playoff meetings (usually after regular-season meetings the same season), with the Packers winning the first three — 35–17 in the slop in Green Bay in 1996, and then 21–7 in San Francisco one season later — before the 49ers won 30–27 in Holmgren’s last game coaching the Packers.

The 1996 Packers beat the 49ers in an epic Monday Night Football game 23–20 in overtime before their playoff win on the way to New Orleans (the site of Super Bowl XXXI, but also Super Bowl XLVII). The 1998 Packers beat the 49ers 36–22 before losing to the 49ers in the playoffs.

Saturday will be the first Packers–49ers playoff game since 2001, when the Packers won in coach Mike Sherman’s first playoff win.

Most seasons, though, the Packers and the 49ers have played each other because of the NFL’s scheduling formula. They would play each other anyway every third season because every team plays every team in one other division of their conference each season. But teams also play the other two teams in their conference that finished in the same place in their own division. And in many seasons, the Packers’ NFC North place was the same as the 49ers’ NFC West place.

One unusual thing about this game is that the 49ers the Packers are playing Saturday are rather different from the team that beat them in week one of the season. That team had Alex Smith, who the 49ers famously picked instead of Cal quarterback Aaron Rodgers, at quarterback. Saturday’s game will feature quarterback Colin Kaepernick (who even more ironically was born in Milwaukee, adopted by parents from New London, and lived in Fond du Lac until he was 4 years old), who will be making his first career playoff start after replacing Smith earlier this season.

The 49ers’ choosing Smith over Rodgers was said to be the choice of then-49ers coach Mike Nolan, of whom the San Jose Mercury News reported, “Nolan was no-nonsense, a strong personality who didn’t like to be challenged. He met with Rodgers and Smith before the draft. He caught a whiff of attitude from Rodgers, and that was that.” Who was the 49ers’ offensive coordinator? Mike McCarthy, who is now the Packers’ coach. Nolan is no longer the 49ers’ coach.

The starting quarterback isn’t all that’s changed, Vic Ketcham notes:

The two teams that will face each other in Candlestick Park on Saturday night are not the same teams that kicked off the season in Lambeau Field.

You’ve heard that said repeatedly, but it’s not just coachspeak, it’s the truth. For starters, six Packers players that were in the starting lineup on Sept. 9 will not be in the starting lineup in Saturday’s divisional-round playoff game.

The Packers of today are in no way representative of the team that was dragged up and down the field on Sept. 9 by an overpowering 49ers offense that made it look easy. The Packers defense that will step onto the field on Saturday night is a legitimate postseason outfit that’s ranked 11^th in the league overall and fourth in sacks per pass play.

Maybe it’ll be that loss to the 49ers in the opener that’ll be the Packers’ greatest ally. Maybe the 49ers will remember how easy it was in the opener and think it’ll be the same on Saturday. It won’t. By halftime, that fact could be a pie in the face for the 49ers.

The Packers might get a little splash of water themselves when they find out how different the 49ers are. That paint-by-the-numbers offense the Packers faced in the opener is gone. Predictability has been replaced by improvisation, in the form of a hot-blooded young quarterback who has brought energy to the team and its fans.

The Packers, meanwhile, have straightened out the offensive line issues that bedeviled them early this season. (The 30–22 season-opening loss was not as close as the score indicated; one touchdown was a Reggie Cobb kickoff return, and the other was when the 49ers were playing the up-two-scores prevent defense.) Saturday’s game features the fifth-best scoring offense against the second-best scoring defense and the 11th-best scoring offense against the 11th-best scoring defense, which makes one think this game will be decided on what the 49ers do on offense.

That begs the question Saturday of whether the Packer defense will be able to deal with a balanced 49er offense. That was supposed to be the issue last week, but the Vikings failed to cooperate because quarterback Christian Ponder was unable to play due to injury, and replacement Joe Webb was unable to play due to inability. If the Packers can bottle up 49ers running back Frank Gore close to as effectively as they bottled up Vikings running back Adrian Petersen one week ago, and if they can force Kaepernick to throw instead of run, they have a good chance of winning. Defensive end Justin Smith will return from injury for the 49ers, but he will be sort of one-armed, playing with a triceps injury, which blunts the 49er pass rush. Candletstick Park, or whatever they’re calling it these days, is not a place where road teams go to die, with the 49ers going 6–1–1 at home this year, coming off their NFC Championship loss to the Giants.

It goes without saying that Rodgers needs to have a good night too. Consider this from ESPN.com’s Kevin Seifert:

A total of 29 quarterbacks have won Super Bowl titles. Only 11 have won multiple championships … and that achievement represents the next step on Rodgers’ career path. His style makes him ideally suited for the historic profile of multiple champions, and he isn’t hiding from the meaning of a second Super Bowl as Saturday night’s divisional-round game at the San Francisco 49ers approaches. …

Rodgers is universally considered one of the NFL’s top quarterbacks (near-unanimous, at least). Still, there are many examples in league history of elite quarterbacks who couldn’t win multiple championships. Look no further than Rodgers’ predecessor in Green Bay.

So what could separate Rodgers? Simply put, he is the least error-prone quarterback in league history.

Turnover totals are among the most reliable indicators of team success, and for quarterbacks, that mostly means interceptions. As you may know, Rodgers has, by far, the lowest interception rate — interceptions per attempt — in NFL history.

Most focus on yards, completion percentage and touchdowns in this fantasy age, but you might not realize that Rodgers has thrown only 46 interceptions in 2,665 regular-season attempts over his career. His corresponding interception percentage of 1.73 is well ahead of the second-best in history, the 2.06 percent of the New England Patriots‘ Tom Brady, and is among the few statistics that don’t have to be curved for the modern-day explosion in NFL passing numbers.

In his seven playoff starts, Rodgers has thrown four interceptions over 253 attempts. That percentage of 1.58 is fourth-best in postseason history. It’s worth noting that in his four most recent games — the final three of the regular season and Saturday’s wild-card victory over the Minnesota Vikings — Rodgers hasn’t thrown a single interception while tossing 11 touchdowns. …

The gang at Cold Hard Football Facts tracks this topic in great detail on their insider site. The correlation between interceptions and victories, especially in the playoffs, is overwhelming.

This season, teams that threw fewer interceptions than their opponents won 80 percent of their games. As playoff intensity ramped up beginning in Week 14, that winning percentage jumped to 95.7. Since Rodgers became their starter in 2008, the Packers have won 90.2 percent of their games in those situations.

Taking care of the ball is especially critical in the playoffs between teams that are presumably closer-matched than in the regular season. In a study updated through most of 2009, CHFF found that a team’s chances of winning a playoff game drops about 20 percentage points with every interception it throws. Teams whose quarterback threw just one interception in a playoff game won only 56 percent of their games. Two interceptions dropped that winning percentage to 31.4.

You might think we’re hashing our way to an obvious conclusion. Interceptions are bad. We know that. But it’s not that Rodgers simply avoids interceptions. Over a five-year span, he has avoided them to a substantially better degree than any quarterback in league history. History tells us the Packers have a better playoff advantage with Rodgers than most any other quarterback. Ever.

Ketcham adds something to a comment that because the 49ers defense is more physical than the Packers’ offense, the Packers will want to quicken the tempo of the game, as they did in Super Bowl XLV:

Make a team that wants to hit think.