From Cold Hard Football Facts:
For me the biggest surprise in the Super Bowl was that Denver really seemed to believe that they could beat Seattle with the same game plan that worked against San Diego and New England. In those games as throughout the regular season, the Broncos excelled in turning 4 yard passes into 10 yard gains.
It all leads us to one big conclusion: sexy offenses like the 2013 Denver Broncos tend to build their portfolio by beating up bad defenses.
Then when the season gets late, when they've consumed a little too much success and suddenly have to negotiate a speed trap of great defenses, these offenses look like your prom date after she disappeared with the guys from the hockey team for an hour: weathered, glassy eyed and not so hot.
Halfway through the first quarter it was clear that a four yard pass was going to be a four yard gain against the Seahawk defense,
This was not a surprise exactly--anyone who watched the Seahawks knew their D was fast and rallied to the ball.
It was a surprise that Manning and Fox apparently did not appreciate this.
The second surprise was that Denver had no Plan B when it was clear that the original game plan was not working