I'd have to invoke the "Scott Norwood Rule" for this one.
It should never, ideally, get down to a kicker at the end of the game. Colts had plenty of chances to put this game away earlier. It was one thing I found super interesting in a Peyton Manning interview several years back, about the value of QBs who can "come back" in the 4th quarter. He said, and I agree, that if you are doing your job as a team, you don't get into that position in the first place. You don't get yourself stuck in a position to make a last minute stop or hope your kicker can pull it out for you.
People really blamed Scott Norwood for missing that SuperBowl kick, but Buffalo had almost four full quarters of football to have made a difference for themselves before it got to that point. Steve Bartman didn't lose that series for the Cubs on his own.
I think it was a bad call personally, but I think it overshadows nearly 4 full quarters of bad calls by Caldwell, Moore and Manning and Co to be honest.
The failures of the Colts in this game was IMHO rooted back to it's ineffective O line and it's inability to sustain a potent rushing attack. The year Peyton Manning won a Superbowl, their line was playing well, their D was tough and they had an actual running game. You win playoff football in the NFL with a power rushing attack and stingy violent defense.
Manning is a great QB, but as QBs get older, you surround them with a power rushing game so they are asked to do more with fewer opportunities instead of more with less capability. Elway won rings when he finally had a bell cow back in Davis.
On Caldwell's end, he just doesn't strike me, from the games that I've seen, as a good time management coach during high stakes situations. To be fair, many many coaches are not, Andy Reid is not very good late in the game. Herm Edwards was kind of comical honestly with his late game adjustments. Dan Reeves, for all this skill and talent, would regularly lose it in the 4th quarter. The Patriots are super lucky to have Belichick, the guy is ice cold in the 4th quarter. He never panics. He has a plan and he sticks to it.
Jeff Saturday, the center, of the Colts has clearly been hurting/declining and I think that has a real ripple effect on Manning and that offense. I truly believe a team that did not rely so much on the pass and could grind the clock wouldn't leave it to their kicker to win it. Also the Colts D was simply not hitting Sanchez enough. It's a lot easier to not leave it in the hands of your time management challenged coach when you can lay some hurt on the opposing QB.