Nowhere was this more apparent than in the second half on second down.
He was 4-for-5 passing with four first downs, and he called three running plays that resulted in first downs over three drives that yielded the Broncos 10 of their 17 second half points. Add in a defensive touchdown to seal the game, the Broncos' offense hit the Steelers every way it could.
Denver only ran three third-down plays the whole second half, and two of those resulted in first downs. They did not punt once.
In running 10 plays on second down, Denver converted seven first downs, including one of Manning's two touchdown passes - a 71-yard catch-and-run by WR Demaryius Thomas. The other touchdown pass came on first down.
Eliminating third down situations stifled the Steelers' pass rush, largely because Manning mixed up runs with passes so well, the Steelers often looked off-balance. The no-huddle negated opportunities to sub in packages, and Manning handed off when strong safety Troy Polamalu dropped into deep coverage, and attacked the Steelers' cornerback opposite Polamalu when he was near the line.
Manning didn't attempt anything deep, keeping his drops three-to-five steps with a release. The Steelers' coverage wasn't strong enough to give pass rushers (who often looked tired) a chance to get to him.
In the first half, they were able to penetrate the backfield, getting two sacks, a fumble recovery and a decent amount of pressure. They also only allowed seven points. Manning was still 3-for-5 passing on third down in the first half, and they converted two third downs on the ground.
Manning often split a tight end (Jacob Tamme) or a receiver (Brandon Stokely) wide, and upon Polamalu or Ryan Mundy approaching the line, drew the receiver in to block, and simply threw to the other side of the blitz.
The Steelers played a lot of man coverage, trying to utilize a bump-and-run strategy, but Manning's accuracy was lethal, finding his receiver in perfect spots.
While the Steelers' defense barely provided resistance to the Broncos as they marched down the field, this was more an issue of them being picked apart by one of the best the game has ever seen as opposed to a massive failure across the board. Coverage appeared to be more of the issue rather than the lack of pass rush (Manning released very quickly, particularly in the second half). With the lack of substitutions denying the Steelers a chance to get more creative in their looks, and Manning wisely keying off Polamalu, he completed an amount of passes atypical to league norms (completion percentage as a league was 60 percent last season, Manning completed 76 percent, and 79 percent of his last 19 throws).
Broncos vs. Steelers 2012: Peyton Manning Debuts in Denver, Leads Team to Impressive 31-19 Win (via sbnation)