Butler was a key cog in that effort, primarily assigned to Welker — his former teammate with the New England Patriots. With his safety blanket in the seam mostly unavailable for the first three quarters, Manning grew increasingly frustrated against the Colts' defense.
Ironically, the seeds for Butler's big night were sown during a 59-35 loss against Welker and the Patriots last year at New England.
"We went back and we watched the New England game last year where he kind of got us," Indianapolis secondary coach Mike Gillhamer said. "I think Darius took it as a challenge that he could get it done, and he did."
The Colts boast the league's sixth-best scoring defense this season — despite playing star quarterbacks Colin Kaepernick, Russell Wilson and Philip Rivers in addition to Manning — and their success has come through the unity of their team.
When strong safety LaRon Landry — who returned with a vengeance against the Broncos — missed four games, reserve Delano Howell ably stepped into his place. And Indianapolis had to call on its bench often against Denver.
Injuries to starting corner Greg Toler, reserve Josh Gordy and Butler forced the Colts to get creative at times. Cassius Vaughn and Sergio Brown were among the players who stepped into the void and made plays, and free safety Antoine Bethea even moved to nickelback at one point in the fourth quarter.
"It was one after another," head coach Chuck Pagano said of the injuries in the defensive backfield. "They'd come off the field and they'd tape something up, go inside, do whatever they had to do and get back out there and do just enough to hold on."
Davis, meanwhile, was the lone constant.
He blanketed Thomas, Manning's top receiver, allowing just four catches on nine targets. And his play is just the continuation of a trend that began in the latter part of 2012.