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When we talk about a legacy, we do so with the assumption there is some finality to it. We assume Denver Broncos quarterback Peyton Manning agrees with us, and he's ready to make the only logical decision remaining at this point.

That decision is to walk away, because there's nothing left to prove.

Being Manning is difficult right now. It's the first time we've been able to say that in, oh, about 20 years.

He shined for the Tennessee Volunteers and was the first overall pick in 1998. His glow didn't fade in the NFL. He's put together 17 seasons filled with brilliance, several of which came after a severe neck injury and multiple surgeries that would have ended most careers.

He's been named the league's MVP five times and been selected to the Pro Bowl a whopping 14 times. The conversation around his legacy is a complicated one because of the many playoff failures that loom over the few triumphs. But he has a second Super Bowl ring now, and he should clutch it tightly during an era when quarterbacks are judged by how many fingers are still bare when they slide on their championship jewelry.

Pushing his career far past its expiration date will only serve to tarnish what Manning has already accomplished and leave us with a stale memory. But it seems Manning is human, and he's behaving like one, too.

On Tuesday, ESPN's Adam Schefter told Mike and Mike of ESPN Radio that "in a perfect world," Manning would like to keep playing.

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Manning has been a quarterback for pretty much his entire existence on this planet, and there's jittery backyard home video to prove it. If we go all the way back to his second year at Tennessee, he's been playing the position at a high level for 20 years (excluding 2011, when he sat out due to injury).

So by pleading with Manning to retire, we're essentially saying this: "Hey, Peyton, you know the athletic thing you've done your whole life, and the unique skill that's allowed you to thrive for so long at the pinnacle of competition in your sport? Yeah, can you just toss that aside for us? Thanks."

It's more than understandable to be hesitant while mulling over the decision to start another chapter in your life, and Manning should take as much time as possible. The annual waffling Brett Favre did for several seasons late in his career showed both how hard it is to pry a quarterback away from his craft and why rushing a retirement decision is never wise.

But there's still a point when normal, human hesitancy crosses into dangerous territory. There's a point when, after wounds from the previous season have healed, the mind can trick the body.

There's a point when delusion takes over. Manning may be reaching that time of blindness if he is seriously considering another season at the age of 40. His body has deteriorated rapidly over the past year, which in turn has resulted in the decline of core skills and attributes needed to be successful as an NFL quarterback.

As Sam Monson of Pro Football Focus quipped, anyone close to Manning who hears about his desire to return should rush him to a device that plays game film. Then flip on his Super Bowl 50 tape.

Manning threw for just 141 yards in that game while completing 56.5 percent of his attempts. He was unable to maneuver in the pocket to escape pressure and was sacked five times.

Sure, he did just enough to produce 17 offensive points, eight of which came after the Carolina Panthers fumbled deep in their own territory and another three of which came after a 61-yard punt return. But he did it while posting a passer rating of 56.6, the third-worst mark among Super Bowl-winning quarterbacks who attempted at least 10 passes, according to Seth Walder of the New York Daily News.

The Broncos defense won that game, and Manning was along for the ride. Which doesn't matter if you have a very 2016 attention span and prefer your quarterback legacies summarized as succinctly as possible. For 2015, we could then go with "Super Bowl winner" for Manning and be done.

But if nuance and even the most basic observation is more your style, then it's clear to everyone Manning is done. Everyone except Manning, it seems.

Look beyond the Super Bowl, and you'll see a season in which he struggled to maintain league-average quarterback status when healthy. Of course, health is the main concern here, as Manning missed six games due to a lingering foot issue, and he may never be truly healthy again. However, if Denver head coach Gary Kubiak was confident enough in backup quarterback (and future starter, if he's re-signed) Brock Osweiler, a healthy Manning still wouldn't have been the playoff starter.

The safest way to watch Manning in 2015 was through parted fingers. He averaged only 6.8 yards per pass attempt, which ranked 25th out of the 28 quarterbacks who took at least half of their team's regular-season snaps, per PFF. Among the same group, his 67.9 passer rating ranked dead last—and it was also easily a single-season career low (his previous low was 71.2 during his rookie season).

But the most remarkable Manning stat from 2015 requires a third, fourth and fifth read to believe it and to take in the wretched smell attached to a once-accurate arm.

Manning's foot injury zapped his power and lower-body leverage. As a result, he lacked the downfield push to be consistently effective as a deep thrower. So, the Broncos focused their passing attack on quick-hitting and conservative throws, which gave their receivers a chance to create gains after the catch.

It worked just fine, though it made this pretty jarring...

Most interceptions in 2015 Quarterback Attempts Interceptions Blake Bortles 606 18 Peyton Manning 331 17 Matt Ryan 614 16 Ben Roethlisberger 469 16 Ryan Fitzpatrick 562 15 Jameis Winston 536 15 Source: Pro Football Focus

Really absorb what you see there, and remember Manning started a mere nine games.

He attempted 283 fewer passes than Matt Ryan. Yet the decaying 39-year-old still finished second overall in interceptions—and somehow ahead of the Atlanta Falcons quarterback.

Manning is only two years removed from setting the all-time single-season passing yards record (5,477 in 2013). That shows how quickly a quarterback's career can go from whizzing by the sign warning of a cliff ahead to careening toward the rocky bottom of that cliff.

But according to Bleacher Report's Mike Freeman, Manning is still wanted around the league, and many have a destination in mind.

Manning won't return to Denver, because intelligently run teams don't commit to paying soon-to-be 40-year-olds $19 million. That's what Manning is owed in 2016, so if he sticks around for one more twilight year, it'll happen elsewhere.

Schefter also said on Mike and Mike that both the Houston Texans and Los Angeles Rams—two teams desperate for even mediocre quarterback play—won't be interested. But right now, that stance seems like a poor poker face.

Manning at, say, 40 percent of what he was during the peak of his career is still an improvement over Brian Hoyer and Case Keenum at 100 percent of what they are now. For the Rams, there'd also be the added bonus of Manning bringing his marquee name to a new market, which would help the franchise generate buzz in its move west.

Peering into the future to see a Rams-Manning marriage doesn't take much of an imagination. But what, exactly, would L.A. be purchasing?

It'd be getting a woefully limited quarterback who lacks the arm strength to effectively throw deep. It'd be getting a quarterback who'd restrict the offense much more than help it. It'd be getting a name, and that's it.

Manning has plenty to offer mentally, which is why he's ideally suited for a front-office position. But physically, it's over, and he needs to walk away now.