They are linked by their Minnesota past, characterized by contrasting personalities, defined by coaching accomplishments.
Ravens coach Brian Billick would be as bold in a board room directing a hostile takeover as he is on the sideline taking apart an opposing defense.
Indianapolis Colts coach Tony Dungy would show the same dignified stoicism whether he's in the final two minutes of a nip-and-tuck playoff game or delivering his son's eulogy.
Billick will angrily scold a player on the sideline; Dungy will critique a mistake with a stare. Billick will strike a pose of defiance at a perceived slight; Dungy will dismiss it with a wave of his hand.
Fire and ice.
Still, while they may be polar opposites to the outside world, these two coaches are more alike than different when it comes to the philosophy of running a football team.
They both place a priority on keeping players fresh for the long haul, ordering shorter practices and less contact. They both treat players as adults, with more freedom and fewer restrictions.
Billick and Dungy will match wits and systems in tomorrow's AFC divisional playoff game in a high-stakes extension of the time they were coordinators with the Minnesota Vikings, challenging each other in training camp.
Dungy became defensive coordinator with the Vikings in 1992. Three games into the 1993 season, Billick was promoted to offensive coordinator, and they coached together on Dennis Green's staff until 1996. For Billick, it was a formative time.
"Watching the way Tony Dungy prepared for an offense - the things he was looking for - created a lot of the fundamental beliefs I have now in terms of the way we prepare, knowing what a defense is looking at," Billick said. "I owe Tony a great deal in that regard."
Dungy described Billick as an analytical, confident coach who "put his players in position to do what they did best and didn't put them in positions to expose their weaknesses.
"I know Brian feels that's what coaching is all about - maximizing guys' strengths and minimizing the things they don't do well. That's how you put a good product out there."
It turned out to be a common trait for both coaches, one of several constructs they took out of Minnesota.
Billick trusted his team enough to give them five days off during the bye week.
"They're both pretty much ultimate player coaches," said Ravens safety Gerome Sapp, who served two seasons under both Billick in Baltimore and Dungy in Indianapolis.
"They're able to relate to the needs of the team, able to adjust to things according to those needs. The actual structure of practice is exactly the same. Everything has a purpose in practice."
Retired Pro Bowl quarterback Rich Gannon, an NFL analyst for CBS Sports now, was the starter for the Vikings in 1992 when Billick signaled in plays to him.
"I could tell this was a pretty talented guy who, if given the opportunity, was going to make the most of it," Gannon said. "He's a dynamic play caller and innovative guy with a great feel for game-planning."
With Billick calling the plays, the Vikings set an NFL scoring record in 1998, launching him to Baltimore as a first-time head coach. By the 2000 season, he had the Ravens winning the Super Bowl.
It was what Billick did after winning the Super Bowl, and after falling to 6-10 in 2005, that most impressed Qadry Ismail, a former Ravens wide receiver who has played under both coaches.
"What's so cool about him is his ability to have the heartbeat of a team," Ismail said. "What frustrated me were the comments [that] he lost that.
"He was smart enough to humble himself, though, and regain that. Not a lot of people can do that ... to be scolded by the owner, write a blog and say, 'I'm going to get back to business,' do it and have the success he's had, and have that spirit of humility."
Since Ravens owner Steve Bisciotti publicly told his coach in the offseason to turn down the volume on his dialogue, Billick has become more Dungy-like. That is to say, he seldom rants and has adopted a lower profile.
Sapp has seen both coaches defuse team crises. At Indianapolis in 2004, Sapp watched Dungy come into the defensive meeting room after consecutive losses - inspired by poor defense - and deliver a simple message.
"He said 'we can go this way as a team and a defense, and this way is going to lead to us not winning many more games,'" Sapp said. "'Or we can go that way and figure out what's wrong and fix it and win a bunch more games.'"
The Colts fixed it and won their next eight games.
In Baltimore this year, Sapp said Billick's decision to fire offensive coordinator Jim Fassel and take over play-calling duties saved the season.
"Because the offense was struggling, I think it was slowly dividing the team," Sapp said. "It shouldn't have, but it does. Coach Billick had to make some tough decisions, and because he made them, people gained a little [more] respect for him in the locker room. I think that was the turning point of our season."
Last year, Billick was noticeably moved at the news that one of Dungy's sons had died. The families were friendly in Minnesota, although Billick and Dungy were not especially that close.
"We had a good time together in the four years I was there," Dungy said. "My oldest kids were the same age [as Billick's]. Denny really encouraged that and did things so the staff had plenty of time together. I had a lot of fun with Brian."
Sun reporter Don Markus contributed to this article.