Overtime had only one play. If it had happened two years ago, when the old overtime rules were still in effect, the game would have ended in exactly the same way. Hence, it is very understandable that the new overtime rules have been overlooked as a factor in the outcome.
However, these new rules may have had more of an impact than at first glance.
With the old rules in effect, overtime games were more of a battle of nerves. The typical strategy was to play not to lose: Getting into field-goal range would be great, but the main aim is to not allow your opponent to get into field-goal range. Conservative offense reigned in overtime periods; after all, a drive with semi-decent field position is just a few first downs away from being in range for the win.
With the new rules, the first possession of overtime has different rules. Instead of being able to win with any sort of score, a field goal allows the other team a possession to respond.
As the Broncos-Steelers Wild Card game entered overtime, the momentum was firmly in the Steelers' corner. They had outscored their hosts 17-3 in the second half, including a game-tying touchdown with less than four minutes remaining.
Let's say the Broncos score a field goal. Then the Steelers, led by the incredibly clutch Ben Roethlisberger and with the momentum, have a chance to tie or even win the game.
If the Broncos saw this coming, it makes tactical sense to play aggressively, as a touchdown ends the game without giving Roethlisberger a chance to retaliate.
Meanwhile, the Steelers may not have adjusted their scheme from the old overtime rules. Hence, they would expect a conservative offense and play to limit such an offense.
The facts support both teams' tactics: In the one play that did happen, the Steelers stacked the box to stop the run while the Broncos attempted a 20-yard pass over the middle of the field. From there, well, you can see that on the replay.
Tebow and Thomas may have made a fantastic play and the Steelers secondary may have dropped the ball on the play, but these new rules are a lingering variable that had a great effect on the outcome of the game.