SANTA CLARA -- What Jim Harbaugh needed was an archenemy, and the ideal candidate was not far away.
That's how this started six years ago -- who could know it would turn into the best coaching rivalry in football and get only bigger and more significant every year?
Back in 2007 when he had just landed the Stanford job, Harbaugh hand-picked then-USC coach Pete Carroll as his foil and bitterest coaching counterpart.
But really, it was probably inevitable that these ultra-ambitious men would end up smacking against each other again and again, continuing with Sunday night's hugely anticipated meeting between Harbaugh's 49ers and Carroll's Seattle Seahawks.
"My own take on it is they're both kind of like the guy with the battery on their shoulder, 'Go ahead knock that off,' you know?" said Rick Neuheisel, who coached against both in the Pac-10 conference.
"It's just kind of their persona. And it shows during the game, it shows every press conference they do. It's all about them. And I don't mean that as an egotistical thing; it's about them in terms of their team.
"I think it's bull elk and bull elk."
Since 2007, Harbaugh and Carroll have beaten each other and baited each other and, yes, respected each other more than anyone else in a football universe that is increasingly defined by them.
They've fed off each other, too.
"I enjoy his company -- very professional relationship," Harbaugh, 49, said of Carroll, who turns 62 on Sunday. "And a lot things made out to be ... what people make them out to be."
It wouldn't have worked if Harbaugh had picked a weakling or neophyte to battle; and it wouldn't have worked had Carroll, 13 years his elder, had dismissed Harbaugh as irrelevant.
This became the best adversarial relationship in sports because they both embraced the tension and targeted each other.
Once Harbaugh got the Stanford job, he put Carroll and USC in his sights, as publicly as possible, because USC was goliath.
"We wanted to raise our program up to that program," Harbaugh said. "That was our goal. Put that goal down, had that in mind, and worked to achieve it."
The early result: As 41-point underdogs, Stanford tripped up top-ranked USC at the Los Angeles Coliseum on Oct. 6, 2007.
"I think that win at the Coliseum was the signature moment for Stanford's reclamation project," Neuheisel said.
"And I just think it kind of defined who Jim Harbaugh has been since the Stanford job and then on into the 49ers job."
Stanford finished 4-8 that season and USC won the Rose Bowl, but the Stanford victory was a message: Watch out USC, here comes Stanford. And Harbaugh.
"It was a cornerstone-type of a win for the program," Harbaugh said Friday.
Two years later, Harbaugh's Cardinal team destroyed USC 55-21, Harbaugh blatantly ran up the score, and the two men had the infamous "What's Your Deal?" exchange at midfield after it was over.
Then Carroll went to Seattle and a year later Harbaugh landed with the 49ers -- together again in the NFC West, with Harbaugh dying to knock off Carroll again.
"No question," Neuheisel said, "just as Pete wants to knock off Jim.
"I think deep down there's mutual respect amongst the two guys. But they're not going to give any quarter, just will not. It's just not who they are."
When Harbaugh signed his deal with the 49ers, according to a 49ers source, one of the first things he said to CEO Jed York was that he was ready to beat Carroll again.
I would guess Carroll was thinking similar thoughts about beating Harbaugh.
Guess what: The Seahawks and 49ers are built along almost the exact same foundations, with great young quarterbacks, physical running games and fast, aggressive defenses.
And Carroll and Harbaugh remain slightly angled and distorted reflections of each other's manias.
Carroll is the eager, sunny motivator; Harbaugh is the fierce, clipped brawler. But they're the same kind of frenzied coach, deep down.
"It may not be so much going to war type of thing (with Carroll) as it is, 'A chance for us to reveal ourselves and to play great and that's what we want to do, make this your career performance today,' " said Stanford director of player development Ron Lynn, who has worked for both men.
"With Jim, it's, 'We're all in, it's only the strong that's going to survive this one, and we're going to be the ones to come out on top.'
"But they're both highly organized; they're both really aware of the strengths and weaknesses of their own team as well as their opponents' and do a great job of getting their teams ready to play."
For the record, Harbaugh's Stanford teams were 2-1 against Carroll's USC teams and Harbaugh is 3-1 as the 49ers coach against Carroll and Seattle. Harbaugh got to the Super Bowl last season, and Carroll has yet to make a trip.
So it wouldn't be surprising if Carroll now is looking at Harbaugh's 49ers the same way Harbaugh looked at Carroll's USC Trojans -- they've got what we want, let's take them down.
The rhetorical skirmishes about whether or not Harbaugh honked at the Seahawks bus after the 49ers' win at Candlestick last year or Harbaugh's perceived criticism of the Seahawks' PED problems ... that's just how it goes when the fever runs this high.
That's the ultimate respect: To be good and to be hated by another good team that can't help it.
"They both have long memories, now," Lynn said with a chuckle of Carroll and Harbaugh. "I know as a competitor you kind of have a short memory, but they both have long memories.
"They can tell you specific plays, specific points in the game when this happened or that happened, that ultimately made a difference in the result.
"And both probably can tell you plays that had no bearing on the final outcome, if you know what I mean."
Harbaugh and Carroll know that they can't win it all without beating their rival first, and they hate that and love that.
If Carroll didn't exist, Harbaugh would've had to create him. To some extent, they kind of created each other.
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