By Tony Massarotti, Boston.com Columnist

In the middle of it all stands Colin Kaepernick, the tattooed quarterback with the arm of a late-inning reliever, the legs of a world class sprinter, and the look of a US Marine.

Conventional wisdom will be on trial when the Niners and Ravens face off in New Orleans on Sunday, so Patriots fans take note. The NFL is changing. Or maybe it has already changed. Sunday’s game will feature running offenses, big-play quarterbacks (in a variety of styles), and hard-hitting defenses, all models for a Patriots team that has fallen short of a Super Bowl title now for eight years running.

If Bill Belichick is most guilty of anything during his time as coach of the Patriots, it is this: resisting some of the changes that have taken place in the league over a period of years. After the Patriots lost to the Indianapolis Colts in the 2006 AFC Championship Game, it was as if Belichick decided that a quarterback like Peyton Manning simply could not be stopped anymore, so the way to win was to fight fire with fire. That offseason, Belichick bought quarterback Tom Brady a toy chest that included Randy Moss and Wes Welker, and the Patriots have generally been a modern day version of Air Coryell.

At least until recently, when the Patriots clearly put greater emphasis on both a more balanced offense and a pass rush, the latter of which they addressed (in theory) with the drafting of defensive end Chandler Jones.

Making his way through a series of radio interviews on Thursday, Belichick disciple and current Atlanta Falcons general manager Thomas Dimitroff offered an array of thoughts on the ever-changing NFL. Asked to name the most important positions on the field after quarterback, Dimitroff came back with, in order, defensive end, cornerback, perhaps safety. Those three positions just happen to be the ones where the Patriots lacked playmaking ability in the AFC Championship Game against the Ravens, particularly given injuries to Jones and cornerback Aqib Talib.

The obvious question: Why has it taken Belichick so long to successfully address those areas? Until Jones was selected, the Patriots had never really drafted someone deemed to be a pure pass rusher. Belichick’s history of drafting corners has been so bad that the team had to acquire Talib during the season by trade. And the deficiency at safety has been so pronounced that Belichick had to take the one reasonably effective corner he did draft, Devin McCourty, and move him there.

Certainly, prior to the 2011 season, Belichick made an attempt to address the Patriots’ shortage of pass rushers by acquiring defensive ends Andre Carter and Mark Anderson via free agency. But the general point is that if Belichick begin molding his offensive personnel and philosophy to the air game following the 2006 season, why didn’t the same changes take place on his defense until years later?

For certain, assuming that the Patriots retain free agent Talib (or replace him with someone comparable), the defense is developing. But one of the questions now concerns whether NFL offenses are reacting, which brings us back to Kaepernick and, for that matter, similarly mobile quarterbacks like Robert Griffin III, Russell Wilson, maybe even Cam Newton.

Think about it. As the game has become more pass happy, newer, younger executives like Dimitroff have put an emphasis on positions like defensive end and cornerback. In turn, some like San Francisco 49ers coach Jim Harbaugh has drafted a quarterback like Kaepernick and then boldly entrusted the team to him despite the relatively error-free play of his predecessor, all because Kaepernick brings a dimension – namely, speed – that allows him to make plays with his legs when he is being chased by those defensive ends or when those corners have his receivers covered. (Or both.)

The Ravens? Their formula is entirely different, a more time-tested approach of physicality on offense and defense, with a strong-armed quarterback who can heave the ball down the field. The Pittsburgh Steelers won multiple Super Bowls with that approach roughly 30 years ago. If the 49ers are faster than the Patriots – and they are – then the Ravens are more physical, which leaves the Patriots somewhere in between.

Of course, the Ravens and the Niners just happen to be the last two teams to have defeated the Patriots this season – both on the turf at Gillette Stadium.

In the coming weeks and months, Belichick must find ways to defeat not just one of those teams and philosophies, but both.