In the 2010 NFL season the Colts finally did away with the "Bend but don't break" scheme that had plagued them during the Dungy years, and made a defense full of talented players into a mediocre unit, and that's being generous. The one time that Dungy let the defense play aggressively the Colts won the Super Bowl.
With Dungy gone Jim Caldwell decides to change the system, and go with a more aggressive, and attacking defense. During the regular the Colts defense undoubtedly gave up yards, but also played faster, and more aggressively.
In the playoffs this new aggressive defense handled the Raven's and Jet's running games effectively. They had no problem stopping two of the leagues premier ground games. The Colts stayed on the attack the entire game, and it proved effective.
In the Super Bowl the Colts defense came out looking like they had in their previous two contests playing fast, aggressive, and shutting down the Saints. Then they started to back off. They began playing "bend but don't break' defense like they had in years past.
The Colts played a lot of soft zone coverage that let receivers catch the ball, but not get YAC. This is the very same defensive philosophy that plagued the Colts during Dungy's tenure. The soft defense allowed the Saints to keep Peyton Manning off the field, and control TOP. The Colts defense surrendered the Colts Super Bowl chances, by reverting to the Dungy defense.