When No. 8 Wisconsin plays at No. 4 Michigan on Saturday, there will be two seemingly polar opposites coaching on the sidelines.

The Wolverines' Jim Harbaugh is about as close as it gets to a rock star in college football. Hardly a day has gone by since his return to Ann Arbor that Harbaugh hasn't made headlines, with his globe-hopping satellite camps, rap video cameos, famous friends and, of course, his Twitter-melting social media jabs.

Then there's the Badgers' Paul Chryst, who's more like a soundboard engineer than a rock star. Chryst can seem almost allergic to individual attention or a jarring quote. Just try to find a viral online moment involving him. He doesn't even have a Twitter account.

Outside observers would think the two coaches have almost nothing in common.

"Understandably so," Chryst said before chuckling.

In fact, Harbaugh and Chryst are not only good friends, but their entire families share close bonds. They might project themselves to the world in different ways, yet their core experiences and beliefs are strikingly similar. It's like a yin and yang situation, if one of those symbols were khaki-colored.

"They're actually wired exactly the same," said Geep Chryst, Paul's older brother. "But if one's a neon sign, the other one wants to be the last light you turn off at night and the first light you turn on in the morning. There's probably a point in the day where you need both types of lighting."

The connections between Chryst and Harbaugh go back for decades. Jim's father, Jack, played on the same Bowling Green team in the late 1950s with Dave McClain, who went on to become Paul's coach during his playing days at Wisconsin.

Jack Harbaugh and Paul's dad, George, both were college coaches, too, and they crossed paths frequently. When Jim got drafted by the Chicago Bears in 1987, he spent his first training camp with the team at the University of Wisconsin-Platteville, where George Chryst was the football coach.

"One of most highly respected, great people this game or this world has ever known," Harbaugh said of George Chryst, who died in 1992.

Wonder how Jim Harbaugh and Paul Chryst are friends? "Our dads were friends, the sons were friends, and it's been a 30-year friendship," Harbaugh said. "If somebody can't get along with Paul Chryst, there's probably something wrong with them." Gregory Shamus/Getty Images

Platteville is also where Jim got to know Geep, who was helping the Bears out as a sort of glorified gofer. Mike Ditka hired Geep a couple of years later as a quality control coach for the Bears. Geep Chryst became a confidant for Harbaugh in Chicago, and they were reunited with the San Diego Chargers in 1999.

Geep was the offensive coordinator there, while Paul was the tight ends coach. The Chargers had just drafted Ryan Leaf No. 2 overall, and they wanted a mentor for the young quarterback. So they traded for Harbaugh, who started 12 games that season.

Harbaugh impressed everybody there with his competitiveness and toughness. Geep remembers him trying to get back into the last regular-season game despite a dislocated hip. San Diego had already been eliminated from the playoffs at that point.

"We thought we were bringing in a wily veteran backup," Geep said, "but instead we brought in a wily veteran starter. Paul saw how Jim was wired, and it brought out the little kid in all of us."

Many of the interactions between Paul and Jim that year centered on Junior Seau, the Chargers' Hall of Fame linebacker who moonlighted on occasion at tight end. Jim and Paul would confer on what the best plays were to get Seau the ball. They had plenty of other things to talk about, as both were Big Ten quarterbacks in the 1980s and members of football families -- Chryst's other brother, Rick, was the commissioner of the MAC, and of course Jim's brother, John Harbaugh, is the Super Bowl-winning coach of the Baltimore Ravens.

"Being coaches' kids gave us a little more in common than the quarterback careers we had in the Big Ten, certainly," joked Chryst, who was a career backup with the Badgers.

"Our dads were friends, the sons were friends, and it's been a 30-year friendship," Harbaugh said. "If somebody can't get along with Paul Chryst, there's probably something wrong with them. That's how I've always looked at it."

Paul Chryst loves how fiery and animated Jim Harbaugh is, but that's just not his style. "I definitely have a competitiveness in me. It fuels you," he said "Yet I think it comes across differently." AP Photo/Patrick Semansky

Harbaugh later hired Geep Chryst as his quarterbacks coach with the San Francisco 49ers. Paul remembers calling Harbaugh before a game from a Big Ten stadium when he was Wisconsin's offensive coordinator and asking for Harbaugh's memories of the place -- he can't remember for sure if it was from Wisconsin's 2010 win at the Big House, but Paul lingered in the press box a little longer after that victory.

Harbaugh also gave Chryst some advice on what to do when he got his first head coaching job. What did those words of wisdom include?

"Nothing that makes for good print," Chryst said, declining to share specifics.

After Chryst got his first head coaching job with Pitt in 2012, he came out to San Francisco for a Rams-49ers game during his bye week. Harbaugh secured him a sideline pass, and Geep gave him a 49ers sweatshirt to wear. Harbaugh wasn't too pleased when, after the game ended in a rare 24-24 tie, Rams running back Stephen Jackson ran up and hugged Chryst on the field. Chryst had coached Jackson at Oregon State.

"Jackson just killed us that day," Geep recalled. "Jim looked at Paul like, 'Of all the games ...' "

That was the legendary competitiveness of Harbaugh coming through, one that's not hard to spot on the sidelines or anywhere else. Chryst is outwardly low-key and soft spoken. You would be hard-pressed to tell the difference in his demeanor between a spring practice and after this season's victories over top-10 teams LSU and Michigan State.

Geep says he's sure Jim will have thought about his Wisconsin pregame speech for weeks, if not longer, hoping for the perfectly profound message to inspire his team. Paul picks his spots to even raise his voice in front of his players. Both will have the same burning desire to win Saturday.

"For Jim, I think that's real for him," Paul Chryst said. "It's why I loved being around him -- he's passionate and he wasn't going to hide it.

"I definitely have a competitiveness in me. It fuels you. Yet I think it comes across differently."

Chryst could never imagine getting in Twitter feuds with other coaches or wearing different sports jerseys in each city on a camp tour like his friend. But of Harbaugh's antics, he says, "He's authentic." That's a description often used for Chryst, too.

"They're consistent with who they are, and their teams respond to that," Geep said. "That's genuinely who Jim is and genuinely who Paul is. They're perfect where they're at and comfortable in their own skin."

It's no coincidence that both of their teams play the same way: tough, physical styles featuring fullbacks and tight ends on offense. No spread stuff here. Just old-school football. Chryst says "you can probably trace that back directly to our dads."

Geep plans to sit in the Big House stands next to Earl Hansen, who was the high school football coach for both Harbaugh and Geep's son, current Stanford backup quarterback Keller Chryst. They'll enjoy watching two old friends project wildly different demeanors on the sidelines while aiming for the same goal.

"It's fun because everybody can see the opposite ends of the spectrum they're at, but deep down they're really going to play a similar style of ball," Geep Chryst said. "To have them square off against each other in a big game, no one appreciates it more than those two."