Manning made the Pro Bowl 11 of his first 13 seasons on the field, and he was first-team All-Pro five of his last eight seasons. His elite passing talent, tireless work ethic and football intelligence put him head and shoulders above the rest of the league time and again.
But entering the 2012 season after losing a year to injury, undergoing four scary neck surgeries and suiting up for a team other than the Colts for the first time in his life, no one knew how much Manning had left.
With eight games played, the answer is clear: Peyton is still Peyton.
But is he still the best quarterback in the NFL?
By the Numbers: Peyton vs. Peyton
Statistically, Manning is having one of his best seasons ever—and that's saying something. Manning's completing 69.5 percent of his passes, the best rate of his career. He's on pace for 4,808 yards, another career best, and 40 touchdowns—second only to his 49-score 2004 season.
Manning's rate stats are sublime. He's throwing touchdowns on 6.8 percent of his passes (behind only 2004) and interceptions just 2.1 percent of the time.
Manning's raw yards per attempt (8.2) and adjusted yards per attempt (8.7) are the second- and third-best numbers he's ever managed. Manning's NFL passer efficiency rating is a sparkling 108.6, behind only 2004's insane 121.1, and his ESPN QBR stands at a career-best 85.36.
Long story short: Manning is having at least the second-best statistical season of his statistically incredible career.
By the Numbers: Peyton vs. the NFL
Of course, passing statistics have been inflating like crazy over the past few years. Pushing 5,000 yards passing is nearly yawn-inducing now, right? Let's compare Peyton's stats against his peers this season.
Fourth in passing yards, third in passing touchdowns, second to Eli Manning in sack percentage.
First in yards per attempt, adjusted yards per attempt, net yards per attempt, adjusted net yards per attempt, passer efficiency rating, ESPN QBR.
At age 36, despite attempting fewer passes than 12 other quarterbacks, Peyton Manning is having the best statistical season of any quarterback in the NFL.
The Eyeball Test: Manning's Form
In the preseason, Peyton did not look like Peyton. His gorgeous spirals had a noticeable wobble, his deep passes were nonexistent, and he looked uncomfortable turning his head to see the whole field.
Early in the regular season, Peyton still appeared to be "pushing" the ball downfield. A disastrous three-interception game against the Atlanta Falcons in Week 2 made it seem like the Manning we saw in preseason was the Manning we were going to get.
But he's thrown only three more interceptions in the six games since then.
Manning's passes don't look like the picture-perfect spirals he flicked at the peak of his prowess, but he still manages to fit wobbly balls into very tight spaces. Like Kurt Warner toward the end of his career, Manning's experience and field vision allow him to deliver timely, catchable passes despite age and injury robbing them of artistry.
Manning and the Broncos staff have done a brilliant job of tailoring the offense to his ability and that of his receivers. Manning has learned to trust his targets to make plays in space, so he saves the downfield passes for when he knows they'll connect.
Manning has been skittish in the pocket, bouncing on his feet and repeatedly patting the ball before making up his mind. This is partly because of the way Manning approaches passing: He likes to stay on the balls of his feet, ready to either move or throw in an instant.
Earlier in the season, it seemed as though he wasn't confident in his pass protection. He'd frequently check down or throw it short, even when better choices were open.
Really, Manning's pass protection has been outstanding. ProFootballFocus currently grades the Broncos offensive line as the best pass-blocking unit.
Throughout the year, Manning has grown more comfortable in the pocket, and he's been looking downfield more often. It's leading to bigger plays, no drop in efficiency and no increase in sacks or interceptions.
Peyton Manning Is the Best Quarterback in the NFL
Recently, I broke down the film of Manning and Drew Brees. It looked like Brees was being more aggressive and just as effective, and Brees is throwing prettier passes too.
However, their head-to-head matchup on Sunday Night Football left little doubt: Manning is playing quarterback as well as, if not better than, anyone else. Further, he's a bigger factor in his team's success than anyone else in the NFL.
The Broncos' upgrade to Manning from Tim Tebow couldn't be more obvious. Tebow needed everyone around him to make plays to win, but Manning is making everyone around him look better.
The Broncos were the 25th-ranked scoring offense in 2011. They're ranked fourth in per-game scoring this year.
With few changes in the skill position players, Manning's making them look like stars. As he continues to get his throwing strength and confidence back, his form should only continue to improve.
Players like Eric Decker, Demaryius Thomas, Brandon Stokley and Jacob Tamme will continue making Manning look good on short routes, and he will make them look good on the deep ones.
I often say there's no such thing as the "best" quarterback, only the "most right" quarterback for a given system. However, Manning's quick adaption to his weakened arm and radical change of offense and teammates proves it: He's the best quarterback in the NFL.