The ball flies over the head of Peyton Manning and into the end zone for a safety. It was all downhill from there. (Kevin C. Cox / Getty Images)

Sometimes, it’s the littlest, simplest decisions that, in retrospect, are so damning.

Take the Denver Broncos in Super Bowl XLVIII, for instance. The day after losing to the Seattle Seahawks, they continued to conduct a post mortem on just where their season went so catastrophically wrong. One possible moment? The decision last week to turn down crowd noise during practice because coaches didn’t think it would be a factor. It was. It epically was, as the first offensive snap from center Manny Ramirez sailed past Peyton Manning for a safety. It was only two points, but the Broncos’ vaunted offense seemed stunned after a season in which it had scored at will.

“That’s the way the start of any Super Bowl is: It’s going to be loud,” Broncos wide receiver Wes Welker, whose resume boasts Super Bowl experience with the New England Patriots, said (via Peter King’s “The fans are going to be yelling. They don’t really know why they’re yelling — it’s just the start of the Super Bowl. We didn’t prepare very well for that, and it showed.”

Coach John Fox has been to Super Bowls, too, but “it’s not an ‘away’ game,” he said (via pool report last week). “The ones I’ve been to haven’t been too loud.”

This one was. It might not register in the top 10 of noisy crowds in Seattle, but it was loud when the Broncos began their first drive 12 seconds into the game. Manning is a quarterback who knows about the advantages and disadvantages of crowd noise — he used it like a maestro in Indianapolis, training Colts fans to bring down the house when opponents had the ball and be quiet as a mouse when he was crafting his plays. But he was up against a wall of sound that swallowed every single “Omaha” he uttered.

“We were using a snap count on the play, but, due to the noise, no one could hear me,” Manning said of the first play. “So really I was walking up to the line of scrimmage to make a change and try get us on the same page. The ball was snapped. Really just an overall, nobody’s fault.”

It was only one play — two little points — but it’s the little things that matter as the games grow in magnitude. Manning and the Broncos never recovered.