SEATTLE, Wash. -- The hip-hop music finally had stopped thumping last week when an assortment of giddy corporate sponsors strolled toward the entrance to the Seattle Seahawks' locker room. The team was wrapping up its first day of an offseason minicamp, but the fun was only beginning for everybody in attendance. A small boy wearing a Russell Wilson jersey dashed onto the field to film a segment with players for the Make-A-Wish Foundation. Hosts from a local radio affiliate sat down to conduct interviews. With players casually walking off the practice field, nobody was racing to find the valet who had parked their cars outside the team's training facility a couple hours earlier.

Seahawks head coach Pete Carroll confidently strode through this scene wearing a red scarf with the words "USA vs. Panama" etched across the front. He was on his way to watch those teams play a soccer match across town that evening, so Carroll told a nearby reporter, "I'm making a strong political statement." The irony was that Carroll probably hadn't heard that another NFL head coach was playing politics and sending more potent messages about 800 miles south of Seattle that same afternoon. They were the type that could easily sour his good mood.

To understand how intense the rivalry between the 49ers and Seahawks has become, all you have to know is what San Francisco head coach Jim Harbaugh said in response to a question about five Seattle players who have been suspended for using banned substances since 2011. Along with saying he "definitely noticed" what had been happening with the Seahawks, Harbaugh added that "you always want to be above reproach, especially when you're good, because you don't want people to come back and say, 'They're winning because they're cheating.'"

Those comments rankled the Seahawks; cornerback Brandon Browner told a local radio station that if Harbaugh were lining up against him after making such a statement, "I'd put my hands around his neck." But they were only more fodder in what has suddenly become the NFL's best rivalry. "I don't like using the word 'hate,' but it's definitely like a heavyweight fight when we play each other," 49ers Pro Bowl linebacker Patrick Willis said. "We're not throwing little jabs that barely hurt. We're trying to knock each other out."

The issues between the 49ers and Seahawks largely exist because of what has happened over the past 12 months. First, there were the games. San Francisco earned a hard-fought 13-6 Week 7 win before being blown out 42-13 in Seattle in Week 16. Even though San Francisco won its second consecutive NFC West title -- and eventually reached the Super Bowl -- those contests served notice about where this series was heading. The first game let the 49ers know the Seahawks were legitimate threats. The second allowed the Seahawks to see just how devastating they could be when everything was clicking.

If those games weren't enough to increase the drama, both teams have helped fuel the rivalry through the media. Harbaugh openly complained about the physical play of Browner and fellow Seattle cornerback Richard Sherman after the first game, telling CSNBayArea.com that those players should have been penalized for illegal contact several times. Yahoo! Sports also reported that Seahawks players were miffed that Harbaugh supposedly waved at them mockingly after that game, a move that made their blowout victory in the rematch all the more satisfying. San Francisco linebacker NaVorro Bowman also threw a log on the fire in April, when he told NFL.com:"I think people like the next best thing. I think people like seeing the challenger get close to the best. ... You have to earn these things. This is their first time being mentioned like that [as a championship contender], in this sentence, and we'll see what they'll do with that."

Seattle cornerback Brandon Browner took exception to Jim Harbaugh's recent comments about the Seahawks. AP Photo/Greg Trott

There actually have been enough comments flying back and forth between the camps lately that the teams have resorted to an even more telling indication of how much they don't like each other: They've tried to be more politically correct. When asked about the rivalry, Seahawks safety Kam Chancellor said, "It's just two good teams facing off against each other twice a year." Niners tight end Vernon Davis downplayed the drama by claiming, "I've never looked at it as a rivalry. I just see it as competing." Seahawks fullback Michael Robinson, who spent four years in San Francisco, said, "I think every team we play in the NFC West is a hard game. This division is starting to get respect for how tough it is."

These are the statements players make when they know even the most innocent remark can be blown up into bulletin board material. The words reek of stern warnings and savvy public relations coaching, and they run counter to the very nature of both teams. The main reason the 49ers and Seahawks have built such a hearty rivalry is becausethey are practically mirror images of each other. They've both built themselves up as hard-nosed, tough-minded squads that won't back down from anybody.

In 2012, both teams ranked in the top five in rushing offense (Seattle was third, San Francisco fourth) and total defense (the 49ers were third, the Seahawks fourth) while relying heavily on young, talented quarterbacks (the 49ers' Colin Kaepernick and the Seahawks' Wilson). "I like their style," Carroll said. "They're coached well and they play like it. They run the ball well. They play good defense. They have a strong kicking game. We have a similar approach to doing things and I think it's a great way to play football. People have changed around the league because a lot of people like throw it, but [being physical] still works for us."

Pete Carroll has acknowledged similarities between his Seahawks and their fiercest rivals, the San Francisco 49ers. Joe Nicholson/USA TODAY Sports

Unlike most NFL rivalries with some sex appeal -- namely Ravens-Steelers, Cowboys-Redskins and Bears-Packers -- the genesis of the 49ers-Seahawks enmity can be traced back to the college level, specifically a Southern California-Stanford game in 2009. The Trojans were a national power at that point, having won two national championships under Carroll's guidance (the NCAA later stripped the school of its 2004 title in the wake of violations). The Cardinal were trying to enjoy their first winning season under Harbaugh while seeking their second win over USC in his first three years as their head coach.

Harbaugh already had made some news a couple of years earlier when he told reporters that he'd "heard" Carroll would only be at USC for one more season. But everybody in the college football world noticed what happened when Stanford beat USC by the score of 55-21 in that 2009 contest. Harbaugh attempted a 2-point conversion late in the game despite leading by a considerable margin. Carroll responded by shaking Harbaugh's hand after the game and asking, "What's your deal?" Though Harbaugh responded with the same question before jogging off, the message had been sent. If Carroll didn't like the results, he needed to find a way to win the next time out. As it turned out, Carroll would leave USC after that season, not facing Harbaugh again until both were in their current jobs.

"You're talking about two head coaches, but you're also talking about human beings here," Davis said. "When they're competing against each other, I'm sure there are some chips on their shoulders because of what happened when they were in college."

The Pete Carroll-Jim Harbaugh rivalry can be traced to their days as college coaches. AP Photo/Matt Sayles

Harbaugh brought that same tenacity to the NFL when the 49ers hired him in 2011, and it has created similar problems for him at times. The most notable moment came in his first season, when Detroit Lions head coach Jim Schwartz angrily chased and confronted Harbaugh after a 49ers' win. It's still a mystery as to what Harbaugh said during the postgame handshake to set off Schwartz, but there's no doubting the opinions that resulted from it. Harbaugh, for better or worse, has a way of rubbing opponents the wrong way.

Some of that comes from his ultracompetitive nature. The rest comes from his legendary quirkiness. This is a man who, as an Indianapolis Colts quarterback, once attacked Hall of Fame quarterback and then-broadcaster Jim Kelly for questioning Harbaugh's toughness. When Harbaugh took over at Stanford, he was so eager to harden the school's image that he flirted with the idea of calling the school's stadium "The House of Pain." Harbaugh even vomited once while running training camp sprints in his first head coaching job at the University of San Diego. He wanted to show his players how far they needed to push themselves to succeed.

Carroll, on the other hand, has built his reputation on energy, charisma and an impressive resolve of his own. He was bounced out of two NFL head coaching jobs (the New York Jets and New England Patriots) before he rebuilt USC into a national power. By the time he hit the college level, Carroll had been turned off by how closed-minded professional owners could be to a coach who had his own unique style of leading a team. Carroll, a Bay Area native, is "California cool" personified, a man who cherishes the Grateful Dead as much as he loves creating intricate defenses and bonding with his players.

The only reason Carroll returned to the NFL in 2010 was because Seattle owner Paul Allen was willing to give him the power to run the franchise any way he saw fit. With the assistance of general manager John Schneider, Carroll overhauled the Seattle roster in his first year and won the NFC West with a 7-9 record. After winning seven games again in 2011, the Seahawks broke out last season. "The end of last year was when things really changed for us," said Seattle wide receiver Golden Tate. "We brought in some big-time talent and you could tell that people were finally expecting us to win. We always knew we could be this good, but now the rest of the world sees it as well."

A 2011 postgame handshake between Jim Harbaugh and the Lions' Jim Schwartz escalated into a confrontation. Leon Halip/Getty Images

Most importantly, the 49ers have witnessed that growth up close and personal. They know what it's like to be a young team trying to find its way, because that's exactly what they were before Harbaugh led them to a higher level. They had obvious talent that underachieved under former head coach Mike Singletary. They know how precious it is to be on top in a league where players change teams continually and windows of opportunities don't stay open for long.

The Seahawks, though they are loath to admit this, also understand that their road to a championship winds directly through San Francisco. "When I came into the league [in 2007], Seattle was the team and then Arizona had its run," Willis said. "But it was different then because Seattle is far more physical now. They're a really good football team, but I also feel this division still belongs to us."

That might not be true for much longer. The most interesting aspect of Seattle's blowout win last season was something that didn't happen. With the Seahawks comfortably ahead late in the game, a number of people along the sideline implored Carroll to run the score up to 50 points, according to Yahoo! Sports. Carroll told the website that he had been "reminded" about how Harbaugh had embarrassed his team in that 2009 USC game. Carroll figured the proper message already had been sent to his division rival.

The only question that remains is how the teams will respond this season, especially now that the stakes are higher and the expectations have become greater. "This has always felt like an amped-up rivalry game for me," said 49ers left tackle Joe Staley. "It's just that now there will be more attention paid to it by everybody else."