For nearly 20 years now, beginning with the last few seasons of the Chuck Noll Era and continuing through Bill Cowher's entire 15-year tenure, the Pittsburgh Steelers have employed the 3-4 defense.
Pittsburgh scouts scoured colleges for undersized defensive ends, guys like Greg Lloyd, Joey Porter and Clark Haggans, that they could convert into linebackers. They sought out defensive tackles who possessed the size and speed components needed to move outside to end in the 3-4. And they always placed a priority on unearthing cornerbacks who would come up from the secondary and support against the run.
But let's say Cowher departs after this season, walks away with one season remaining on his contract and takes a year or so off to recharge his batteries. And let's say the Steelers replace him with a new coach whose philosophies and personal preferences run completely counter to those established in Pittsburgh over the past two decades, a guy who absolutely abhors the 3-4 concepts.
What happens to the Steelers' current defensive personnel? Or to current coordinator Dick LeBeau and his trademark 3-4 zone-blitz schemes? Heck, what becomes of the 3-4 defense in Pittsburgh, period, under a new guy who might demand the more conventional 4-3 front?
"Now you see some of the reasons it's so hard to let a coach go and to pick a new one," said one longtime NFL executive whose team is not considering a coaching change in the coming offseason. "It means an upheaval at a lot of levels. It changes people's lives. It changes personnel and [schemes]. It changes just about everything you do. It really is a traumatic event. Which is why you agonize so much over it."
The time of agonizing for owners who are considering a coaching change begins with the conclusion of the regular season this weekend. Because there were 10 coaching changes after the 2005 campaign -- the average since the 1970 merger has hovered around seven -- there figures to be significantly less attrition during this year's firing-and-hiring cycle. Unlike last year, there probably won't be blood running through the NFL's streets within a few days of the season's end.
Yet there will be change, for sure, and owners and general managers in some league precincts will have to go through the process of identifying the best fit for their franchise.
"Different [coaches] do it different ways. But the most important factor in success is finding a coach who has something compelling about his nature. Something that compels guys to play hard for him. There has to be that kind of connect."
-- Former NFL QB Hugh Millen, who played for seven different head coaches during his nine-year career. "
And, make no mistake, fit does make a difference in the hiring end of things.
Not all that long ago, the process operated this way: If the coach you were dumping had been known as a "players' guy," you hired a hard-ass to replace him. If the guy handed his walking papers was a martinet during his tenure with a team, his successor was typically someone with a more benign approach. OK, so that's oversimplifying the process, we agree. But there was an element of a white hat-black hat mind-set that existed in the league.
The emphasis now is on finding a coach for whom the guys in the locker room will play, a sideline boss for whom the charges will fall on the spear, if need be.
"Different [coaches] do it different ways," said former NFL quarterback Hugh Millen, who played for seven different head coaches during his nine-year career. "But the most important factor in success is finding a coach who has something compelling about his nature. Something that compels guys to play hard for him. There has to be that kind of connect."
But there also has to be a philosophical connection, too, and some sense of how a new coach will handle the old leftovers, the residual players, the old offensive and defensive systems, the scouting staff and just about everything related to football. That's where things can get pretty tricky for both sides at the interview table.
In an age of instant gratification when every owner's ego drives him to want to be the guy standing on the riser and clutching the Vince Lombardi Trophy after the final game of the year, no one wants to hear from a candidate that it might take three seasons to retool a team to the coach's desires. Coaches also understand that the average shelf life in the league for their profession has been diminished because of the pressure to win as quickly as possible.
But change begets change in the NFL. And casting off one head coach and hiring another means that the die has to be smashed and a new design forged in the image of the replacement.
In Atlanta, a new coach might not want to retain the zone-blocking schemes installed three years ago by Alex Gibbs, techniques that rely on smaller, quicker linemen, but which have yet to demonstrate an ability to consistently protect the passer. Two summers ago, New York Giants coach Tom Coughlin decided he wanted more quickness at defensive end, so he moved Osi Umenyiora into the starting lineup and had Michael Strahan drop his weight into the area of 255 pounds. If Coughlin is fired, his successor might not want such smallish players on the flanks of his defense.
Should Dennis Green be fired in Arizona, his successor might want a more run-based offense, so what does he do with prolific receivers such as Anquan Boldin and Larry Fitzgerald? The Cleveland Browns invested a lot of time and money transitioning to the 3-4 front Romeo Crennel preferred, and he could be dismissed after only two seasons. Does that mean sacking the 3-4 defense and divesting the Browns of some players acquired specifically to play it?
"It's the age-old question," said the team executive who earlier cited the agony of changing coaches. "Are you looking for a new coach who can fit with the players and systems already in place? Or do you junk what you've got, just cash out the human inventory, and try to find players who fit better with what he wants to do?
"There's really no easy answer."
Len Pasquarelli is a senior writer at ESPN.com.