Former NFL quarterback Tim Hasselbeck, now a studio analyst for ESPN, said teams with established veteran quarterbacks such as New England's Tom Brady and Denver's Peyton Manning rarely, if ever, call plays that the quarterback can't adjust. For some teams, the play call includes a "kill" or "alert" play — essentially a backup play if the first one will be unsuccessful.

"Not every play is designed to be successful against a certain look or a certain coverage or a certain blitz," Hasselbeck said. "So teams like the Patriots or the Broncos, they won't just blindly call a play. The call won't come into the quarterback, he'll leave the huddle and say 'Hut.'"

Hasselbeck said he didn't see any reason why Flacco wouldn't have similar leeway at this point in his career.

"Quarterbacks who are good at the line of scrimmage can solve so many problems," he added.

In many cases, though, when the quarterback starts yelling and gesturing at the line of scrimmage, he isn't scrapping the entire play, like switching to a screen pass when staring down an all-out blitz. He could just be changing blocking assignments, flipping the direction of a running play or shortening his drop to sync up with a blitz-beating hot route.

"I think audibles, the way people talk about it, it's overrated," Flacco said. "It's a handful of times in a game where defenses really do something to take something away. A lot of the times, people probably don't even know if I'm doing it. A lot of the time we have audibles, but the first play is there so you don't need to audible."

But late in the Super Bowl, with the football world watching, it was one of those times when the defense dictated a change. The throw was accurate and the catch was clutch. Flacco's audible was also significant, and not just because he was allowed to do it.

"I think he's one of the best in the league at communicating and getting us into the right looks that we need to be in," tight end Ed Dickson said. "That's a testimony to him and the growth that he's had since he's been in the league."