Every once in a while over his final two years as Oregon's head coach, Chip Kelly would travel the 500 miles from Eugene to San Francisco to pick the brain of a friend and former rival. Jim Harbaugh had gone from Stanford to the 49ers, had made the same college-to-NFL jump that Kelly later made when the Eagles hired him, and the two were finally free to exchange ideas about offensive schemes, particularly Kelly's version of the read-option.

So what were those conversations like?

"Football talk," Harbaugh said on a conference call Wednesday in that halting delivery of his, as if he were searching for either the right word, the right dash of sarcasm, the right amount of evasiveness - or all of the above.

"He's a great guy to talk to, talk football to. I enjoy him as a person. He's got all the qualities I like in football coaches, a football guy."

What are some of those qualities?

"Just a football guy," he said. "That says it all. Football man. Encompasses all the things I like about football people."

Sunday will mark the first time that Kelly and Harbaugh will have coached against each other since their days in the Pac-10, when they split their two games - Stanford upsetting No. 7-ranked Oregon in 2009, the Ducks routing the Cardinal by 21 points the following season. Just as the Seahawks' Pete Carroll has, Harbaugh and Kelly have gone a long way in shattering the stereotype that a college coach can't survive or thrive in the NFL, and each football man has done it in his own football way.

"I don't lump everybody in," Kelly said. "Everybody tries to paint with one brush and color everybody one thing. So when one college coach isn't successful, 'college coaches can't do it.' But when a college coach is successful, college coaches can do it. I think you've got to look at the individual."

In shepherding the 49ers to 37 regular-season victories, three NFC championship games, and a Super Bowl berth during his tenure, Harbaugh has created a different persona from Kelly's. In less than two years with the Eagles, Kelly has become the league's most creative offensive mind, and his manner on the sideline and in his interactions with the media - his countenance usually impassive, the words tumbling out of his mouth like beans from a bag - reinforce the image that he talks fast, thinks faster, and is always a step ahead of everyone else.

With his pleated khaki Dockers, the pained facial expressions, and snarling intensity that have earned him the chance to star in a couple of funny TV commercials, and his belief that football games are won primarily with a power running game and an intimidating defense, Harbaugh could hardly strike a more dissimilar pose from Kelly's.

"He's got more of an old-school, blue-collar approach," said Eagles tight end Zach Ertz, who played for Harbaugh at Stanford. "He wants to out-physical everybody, out-tough every opponent. He's going to set that tempo every day at practice. That's kind of a big thing."

Of course, Harbaugh did introduce a recent innovation to the NFL, and it can be traced to his time coaching against and speaking with Kelly. Remember: The 49ers already had reached one NFC title game with Alex Smith as their starting quarterback and could have reached another with him, yet Harbaugh was willing to replace Smith with Colin Kaepernick and make the read-option and "pistol" formation staples of San Francisco's offense.

"From the looks of it, they're very different," Ertz said of Harbaugh's and Kelly's offenses, "but the mentality's the same. Both teams are kind of run-first. The run game's going to set up everything else: the pass game, the screen game. Time of possession is different, obviously. We want to run a lot of plays. They don't really care how long the play clock ticks down. But at the same time, they're both very good."

The question that both Kelly and Harbaugh have yet to answer is whether their coaching styles, as successful as they've been so far, should come with expiration dates. The 49ers are 1-2, and reports and rumors are swirling that Harbaugh might be losing the locker room, that he might return to college coaching, that this terrific run he started the franchise on in 2011 might be in danger of ending already. And while the Eagles are 3-0, Kelly this week experienced the first public pushback against his grueling practice schedule, when cornerback Cary Williams suggested that the Eagles should throttle back the pace of their daily workouts.

These aren't necessarily crises, for either coach. But they are situations worth monitoring, just to see how Harbaugh and Kelly handle them. After all, a true football man adjusts, in his own way.