The NFL's best, most intense, most fascinating rivalry didn't amount to much three years ago.
It's one of the most unique rivalries the league has ever seen, since it extends from the fan bases to the players to the front offices -- and, more than anything, to coaches Jim Harbaugh and Pete Carroll.
It all started when they were rival college coaches, with their infamous "What's your deal?" exchange at midfield after Harbaugh's Stanford Cardinal ran up the score on Carroll's USC Trojans in 2009. Since then, various amounts of fuel have been poured onto the flames, with moments such as Harbaugh's taking a subtle shot this past summer at the Seahawks' string of PED suspensions – and prompting Seattle players Brandon Browner and Golden Tate to fire back with how much they wish they could enact some physical revenge on Harbaugh if they ever got to line up against him on the field.
But more than anything, this rivalry has earned top billing because of how darn good these teams have become.
These NFC West foes are the two best teams in the conference -- maybe the two best teams in all of the NFL -- and they're the only obstacles left in each other's path to the Super Bowl as they prepare for Sunday's NFC Championship Game.
"There's no love lost and there's no love found," Seattle cornerback Richard Sherman said in his typical loquacious manner this week, not shying away from the storyline that has dominated both teams' camps.
But while Sherman has a tendency to take things over the top on occasion, you've got to give him credit for perfectly capturing the spirit of this surging rivalry this week.
"I don't hate anyone," Sherman said. "But passion, definitely. There'll be strong dislike. It's playoff football, so there'll be a lot of intensity anyway, even if we weren't two teams very familiar with each other. But there's going to be a lot of chippiness in a hard-fought game. The two best teams in the NFC are the ones that are here."
Sherman later added, "If we were both 4-12, it wouldn't be so intense."
The rivalry is probably as personal for Sherman as anyone else. He played under Harbaugh at Stanford, and Sherman's father, Kevin, once told Sports Illustrated that transferring from wide receiver to defensive back "saved" his son because he didn't have to interact with Harbaugh as much.
Last year, Sherman referred to Harbaugh as a "bully" after Harbaugh complained about the Seahawks' defensive backs getting away with too much contact. And Sherman admittedly lobbied Carroll to run up the score on the 49ers in a 42-13 Seattle victory in 2012.
The rivalry has certainly been juvenile at times -- and not just among the Seahawks fans who flew a "12th Man" flag over the 49ers' stadium or the 49ers fans who paid for a billboard outside of Seattle, touting San Francisco's championship history.
Harbaugh himself was accused by Sherman and Seattle safety Earl Thomas of honking and mockingly saluting at Seattle's team bus on its way out of San Francisco in 2012, though Harbaugh has denied it. And San Francisco assistant coach Greg Roman was once heard shouting, "Merry Christmas!" inside the Seattle press box after a 49ers victory there in 2011. Even Harbaugh's wife, Sarah, once admitted on a television interview that, "I really don't like Seattle at all."
But underneath all the silly exploits and the trash-talking that capture headlines from time to time, there is also -- believe it or not -- a respect level that has grown between these two teams over the past three years since Harbaugh took over as San Francisco's coach.
Each recognizes that the other is its stiffest competitor.
San Francisco linebacker Patrick Willis compared the rivalry to a "heavyweight fight" this past summer, saying, "We're not throwing little jabs that barely hurt. We're trying to knock each other out."
And Willis reiterated this week that "there's no question there's a lot of hostility between us."
Willis did add, however, "If we weren't in this race right now, there'd be no doubt that if they were playing against someone else, I would wish them well, because it's in our division. But it's us playing, so there's not going to be any like at all there."
Adding to the unique nature of the rivalry is the striking similarities between the two teams, which value hard-nosed, physical defense and a power run game above all else -- and which both reshaped their identities by adding electrifying young quarterbacks, Russell Wilson in Seattle and Colin Kaepernick in San Francisco, to the mix last year.
And more than ever this year, the front offices keep poaching players from the back end of the other team's rosters -- which is probably an indication of the bad blood between the franchises, but also an indication that they simply have the same taste in players. After all, former 49ers general manager Scot McCloughan, who helped build a good chunk of San Francisco's roster, is now an assistant in Seattle's personnel department.
The teams' personalities are a little different -- they tend to mirror the personalities of their head coaches. Harbaugh is as intense as it gets, while Carroll keeps it loose. San Francisco is more buttoned up, while Seattle's players are by far the more outspoken and vocal ones. They're more of a "chip on our shoulder" team that many observers believe is still clamoring for some level of national respect.
Over the past two years, the home team has won each game in the series. Seattle has some bragging rights because both of its wins have been blowouts. But the 49ers hold the ultimate bragging rights since they reached the Super Bowl last year.
There aren't too many examples of the bad blood spilling over into on-field fisticuffs or cheap shots. They have, however, managed to rack up a combined 19 flags for unnecessary roughness, unsportsmanlike conduct or taunting during their past six meetings, as their physical styles and intensity are constantly on display.
When asked if he enjoys the rivalry after a draining 19-17 49ers victory last month, Harbaugh said, "Enjoy it? That's not the word I'd use. It feels like you go to the dentist chair and 3 ½ hours of getting root-canal work done. They're tough. These games are only for the tough."
Both Harbaugh and Carroll have tried to downplay the animosity between their teams -- and certainly between themselves. Harbaugh, who often seems to put on an aloof front in a calculated manner, said this week: "Animosity? No. Erroneous."
But even a newcomer to the rivalry such as Boldin could instantly recognize what he became a part of. After all, he was part of a similar slugfest for years between his Baltimore Ravens and the Pittsburgh Steelers.
"It'll always be that way when you have two good teams in the same division," Boldin said. "You play each other a couple times a year, and if you're good enough, possibly three times a year. It was the same way when I was in Baltimore playing against Pittsburgh.
"You respect each other as foes, but there is really a dislike."
ESPN.com Seahawks reporter Terry Blount and 49ers reporter Bill Williamson contributed to this report.