What's the common denominator of those teams mentioned in the OP? Those teams have ******* heart, particularly the first two, in spite of being overwhelmed by other, more talented teams.
I vividly recall Todd Haley in his post-game press conference after the Houston game making mention of how a bunch of his players were sobbing in the locker room following the tough defeat. That's a culture change right there, not too long ago it was all about D-Bowe and his making it rain on 'dem hoes with his 'pimp' service, or whatever. Not anymore.