The late Al Davis, the Oakland Raiders czar, used to have a theory that the shelf life of an NFL coach was about 10 years. After that, Davis believed, the coach's message grew stale and tired. Players tuned him out.
Davis pushed out John Madden, whose regular-season winning percentage is the NFL's best in history, after 10 years. He got rid of Tom Flores after nine years. Across the Bay from Oakland, the San Francisco 49ers shoved aside Hall of Fame coach Bill Walsh after 10 years. They pushed out George Seifert after eight.
Among them, those four coaches won eight Super Bowls in less than two decades between 1976 and 1994.
There is considerably more evidence.
Chuck Noll coached the Pittsburgh Steelers to four Super Bowl titles in his first 11 years with the team, then coached another 12 years without reaching another, winning only two playoff games in that time.
Look around the NFL landscape today and you see several of the league's longest-tenured coaches conceivably nearing the end of their shelf life.
Bill Belichick shows no sign of slowing down in New England, especially as long as Tom Brady remains his quarterback, but the other four teams whose coaches are in at least their 10th year are struggling:
Pittsburgh Steelers: Mike Tomlin
Approaching Thanksgiving, none of those four teams are over .500.
Except for Lewis, the coaches on that list all have won a Super Bowl.
In fact, only two coaches in the Super Bowl era lasted a decade without winning a championship and then eventually broke through -- Tom Landry and Bill Cowher -- a factoid that does not bode well for Lewis and the Bengals.
Davis' theory, and others have agreed, is a simple one. It's not so much that the coaches get worn out, although some of them invariably do, but that the players simply tune them out after hearing the same talking points and enduring the same routine for so long.
Of course, Davis' career mostly spanned an era when long-term roster stability was largely a given because there was no free agency in the NFL. Player mobility has changed the equation to a degree, simply because the coach is preaching to a roster that most years will have significant turnover.
That is at least one part of the reason Belichick has proved an exception to the 10-year rule. Of course, it helps that he has a future Hall of Fame quarterback leading his team, but also, the Patriots have done a terrific job through the years of turning over their personnel so they have had different receivers, runners and defensive leaders who haven't had the chance to get bored listening to the coach.
In part, that's why Walsh and Seifert established the San Francisco dynasty with their back-to-back successful runs. The 49ers started with Joe Montana at quarterback and finished with Steve Young. They began with Dwight Clark and Freddie Solomon as receivers and transitioned to Jerry Rice and John Taylor. Their defense had Ronnie Lott at the start and Deion Sanders at the end.
Perhaps this history simply means that an old corollary needs to be revised, the one that says coaches are hired to be fired. Maybe it needs to be reworded to read that coaches either get fired or get elected to the Hall of Fame, because that was the destination in recent years for coaches like Tony Dungy, Bill Parcells, Marv Levy and Madden, none of whose career ended with a pink slip.
The list of Super Bowl-winning coaches who have been fired in the last couple of decades included Shanahan, Coughlin, Seifert and Jimmy Johnson, all of whom won two Super Bowls, plus Brian Billick and Jon Gruden. Clearly, the glow of championship success only goes so far in job security, which is why Payton, McCarthy and Tomlin probably shouldn't be making too many long-range plans - although the Steelers haven't fired a coach for a half-century and Green Bay GM Ted Thompson is hardly the impulsive type, either.
There is a flip side to this coach's shelf-life issue, too, and in the last couple of decades that has worked well for coaches. Used to be that once a coach got fired from a job, that was it, which helps explain why, for more than three decades of the Super Bowl era, only two coaches, Shula and Weeb Ewbank, won a championship with their second team.
But as player movement became routine, so has coach movement. They now seem to learn on their first job and improve on their second, which may be why most recent Super Bowls have been won by recycled coaches - a group that, of course, includes Belichick, he of the '90s struggles in Cleveland.
The last three winning Super Bowl coaches were all fired from a previous job. From the looks of the current NFL standings, there could be some more big name coaches on the unemployment rolls in January.
--Ira Miller is an award-winning sportswriter who has covered the National Football League for more than five decades and is a member of the Pro Football Hall of Fame Selection Committee. He is a national columnist for The Sports Xchange.