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The NFL defines a "deep pass" in its official play-by-play as any pass that travels more than 15 yards downfield in the air.

As an experiment, go outside and measure off 46 feet, slightly more than 15 yards. You probably won't have to go beyond your property line. Then, throw a football to a friend or family member that far away. It probably won't be too difficult, and chances are you won't feel like John Elway after completing the pass.

OK, hotshot, 15-yard passes usually travel much farther than 15 yards; a 15-yard sideline pass actually travels about 30 yards, through the miracle of the Pythagorean theorem. The point is that defining a deep pass is tricky. Fifteen yards is too short, but 40 yards is too long: You wind up trying to grade a quarterback's deep passing ability on just a dozen bombs per year. The Football Outsiders Game Charting Project recorded just 351 passes longer than 40 yards in 2014 (all yardage totals in this article are based on air length; no screen-and-YAC plays allowed), 315 in 2013. At a rate of 10.4 extra-long bombs per team per year, there just aren't enough plays in the data set for any serious analysis.

So let's set our threshold for a deep pass at a Goldilocks minimum of 20 yards: long enough to eliminate many across-the-yard tosses while still common enough to provide a robust set of over 4,200 passes in the last two seasons to statistically analyze.

All data in this study comes from the 2013 and 2014 Football Outsiders internal databases, with some 2012 data added to illustrate a point here and there. Our goal is to determine the best "deep passers," which is a little vague. We aren't measuring pure arm strength, but instead the skill set needed to consistently complete passes 20 yards downfield: accuracy, velocity, touch, timing, decision-making. The best of the best deep passers all have a variety of drivers and irons in their bags. We're also not pretending that we can isolate critical variables like the receivers, the offensive line, the coach, the opposing defenses or the game situations, though end-of-half and end-of-game Hail Marys have been eliminated. We will talk about those things when discussing the data and making final decisions, but the data itself is raw, so you can draw your own conclusions.

We'll get to the top-10 list at the end. Let's take the scenic route through the Hall of Famers, up-and-comers and others to get there.

The Big Five

Most of you aren't itching to see the deep-passing totals for Josh McCown or Blake Bortles. You are here for Tom Brady, Peyton Manning and the big guns. So let's start with the superstars:

Deep Passing Stats: The Elite Quarterback Att Comp Yards TD INT Comp % Yards/Att Tom Brady 136 38 1238 7 5 27.9% 9.1 Drew Brees 143 55 2049 21 6 38.5% 14.3 Peyton Manning 148 64 2238 19 7 43.2% 15.1 Aaron Rodgers 95 49 1814 13 3 51.6% 19.1 Ben Roethlisberger 153 56 1819 15 9 36.6% 11.9 NFL Average (16 games) 133 45 1540 11.4 8.9 33.6% 11.6 Football Outsiders Game Charting Project

Aaron Rodgers completes 51.6 percent of his deep passes. That's a Holy Cow, tweet it, discuss it, stand-in-awe-of-it statistic. Keep in mind that 20 yards downfield, completion percentage is an important statistic, not an inflated one. There are no screens or dump-offs padding the percentages. Rodgers' deep passing completion rate is less than six points below Geno Smith's overall career completion rate. It should probably be no surprise that Rodgers will be among the best deep passers when we finalize the list at the end of the article. (Remember that Rodgers missed half of 2013, depressing his raw totals considerably.)

Peyton Manning doesn't have a great reputation as a deep passer, but then again his "reputation" has become a big bucket of crazy over the years. No one else in the NFL averages two deep completions per game. Remember that we are measuring a set of skills, not pure fastball velocity.

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Drew Brees has thrown more deep touchdowns than any other quarterback in the NFL in the last two seasons. He still may be the best play-action, 30-plus-yard bomber in the NFL, and he uses location and timing to make up for lack of pure power.

If I could choose just one quarterback to get me out of a 3rd-and-19 jam—and Rodgers was shooting an insurance commercial—it would probably be Ben Roethlisberger, who can stand in the pocket against Sauron's army and blast a fireball at his target. That said, Big Ben throws more deep passes than the other legends but enjoys it less, with a higher interception rate and lower completion rate. Then again, maybe he throws deep so often because he is so darned skilled at it, resulting in a dip in his rate stats when he attempts (and occasionally completes) passes Peyton and Brees would shy away from.

Tom Brady and his Super Bowl rings don't care what we think of his deep passing ability. Which is a good thing, because Brady does not throw deep often nor particularly well.

The Young Guns

While we are settling arguments and embracing debate, let's move from the legends to the up-and-comers. How do Andrew Luck, Russell Wilson, Colin Kaepernick, Andy Dalton and others stack up as deep passers? Here's the data:

Deep Passing Stats: The Young Guns Quarterback Att Comp Yards TD INT Comp% Yards/Att Andy Dalton 133 42 1581 14 14 31.6% 11.9 Colin Kaepernick 131 44 1388 9 6 33.6% 10.6 Andrew Luck 152 51 1815 16 8 33.6% 11.9 Cam Newton 124 31 1031 10 6 25.0% 8.3 Ryan Tannehill 119 27 933 3 10 22.7% 7.8 Russell Wilson 121 49 1694 11 8 40.5% 14.0 Football Outsiders Game Charting Project

Russell Wilson and Andrew Luck are a cut above the other young guns, as you might expect. Wilson has better rate stats. Luck threw more deep passes than any quarterback but Roethlisberger in the last two seasons; only Brees and Peyton threw for more deep touchdowns.

Matt Slocum/Associated Press

Wilson's deep passing production fell from 2013 to 2014. His total yardage dipped from 940 to 754, his touchdowns dropped from seven to four and his completion percentage declined by a few points. Wilson lost Golden Tate and other important receivers between 2013 and 2014, of course. Luck's deep passing totals exploded, from 594 yards in 2013 to 1,221 last year. There's no clear winner between the two. What's most enlightening, as we will see in the next chart, is how superior both Wilson and Luck are to many of the veteran quarterbacks in higher tax brackets.

Andy Dalton has a bad rep as a deep passer, but interceptions are his main problem. Dalton heaves too many floating jump balls in A.J. Green's general direction, but he is also capable of fitting 20- to 25-yarders into tricky spots.

Colin Kaepernick's deep passing statistics survived last season's collapse unscathed; when he actually decides to throw deep instead of running around and waffling in the pocket, he's pretty good at it.

Despite his pure skills, Cam Newton is a poor deep passer. His numbers were actually worse in 2013, when he had Steve Smith and Ted Ginn Jr. to throw to, than they were last year, when he was relying on Kelvin Benjamin to remember which route to run.

The stats bear out Ryan Tannehill's reputation as a reluctant, tentative downfield passer; whether the problem is Tannehill or the system is irrelevant, since both are back in Miami this year.

The Veterans

We had the leaders, then the chase group, and now it's time for the peloton! (Yes, I watch cycling when there's no football. It's soothing.) Some of these established veterans have Super Bowl rings, others have impressive statistical accomplishments and complicated histories, and a few just have big paychecks and spotty reputations. Do any of them have the chops to rank among the NFL's best deep passers?

Deep Passing Stats: The Veterans Quarterback Att Comp Yards TD INT Comp% Yards/Att Jay Cutler 137 50 1758 14 8 36.5% 12.8 Joe Flacco 149 37 1409 8 7 24.8% 9.5 Eli Manning 133 43 1484 9 13 32.3% 11.2 Carson Palmer 102 32 1090 9 6 31.4% 10.7 Philip Rivers 131 53 1681 16 10 40.5% 12.8 Tony Romo 102 39 1420 12 3 38.2% 13.9 Matt Ryan 106 40 1310 8 11 37.7% 12.4 Alex Smith 66 17 571 3 2 25.8% 8.7 Matthew Stafford 141 32 1422 10 12 31.1% 10.8 Football Outsiders Game Charting Project

Philip Rivers may have the best timing on deep passes of any quarterback other than Peyton Manning. His arm is good, but his throws are more remarkable for their ability to thread needles between converging safeties or just past the reach of well-positioned cornerbacks.

Ann Heisenfelt/Associated Press

It's not fashionable to give Jay Cutler credit for anything these days. But he flat-out throws footballs very well, and that translates into deep passing stats that are far more impressive than his overall stats.

Tony Romo is also buried under layers of narrative, though no one has ever accused him of being incapable of ripping off deep passes (in the first three quarters, anyway). Romo has the lowest interception rate of any regular starter for the past two years. Take that, narrative!

Matt Ryan and Carson Palmer fall right around the league average for deep passing. Eli Manning falls a little short, primarily because of his knack for deep interceptions. Really, most of these veterans hover around the league norms in most categories, because they are the ones establishing those norms. The "veteran" category shows the benchmarks that coaches expect from the established starters who earn the big bucks: about 25 deep completions per season, a completion rate above about 35 percent, at least 40 yards per game generated by deep completions and not much more than an interception per month.

A few surprising veterans fall short of those benchmarks. Matthew Stafford probably has the NFL's strongest arm, a beautiful release when he wants it to be beautiful, and Calvin Johnson racing and leaping to turn minor errors into completions. Considering his assets, Stafford's deep passing numbers are disappointing.

Joe Flacco earned a reputation as a NASA satellite launching system early in his career, but the moonshot bombs started yielding diminishing returns two years ago. Flacco still generates more pass-interference yardage on 30-plus-yarders than most quarterbacks—Torrey Smith's defenders were flagged for 229 yards on 11 penalties last year, 100 more yards than any other receiver—but you don't crack our deep passing list by almost connecting with receivers.

Tom Puskar/Associated Press

Poor Alex Smith. His numbers, as we are about to see, look like those of EJ Manuel or Kirk Cousins, not the numbers of an established starter with a playoff pedigree. Even if Smith gets graded on a curve for his weak receiving corps over the last two seasons, his stats are so dismal that he earns the title Worst Deep Passer in the NFL, hands down.

The Rookies

Rookies are generally not very good deep passers—even rookies with cannon arms usually mix some impressive bombs with dumb interceptions and a lot of indecision—and the top rookie quarterbacks of 2014 did not arrive with Howitzer reputations (except for Johnny Manziel, who attempted just two deep passes). No rookie will crack our final list, but let's see how they fared:

Deep Passing Stats: The Rookies (2014 Only) Quarterback Att Comp Yards TD INT Comp% Yards/Att Blake Bortles 44 12 411 3 3 27.3% 9.3 Teddy Bridgewater 45 15 447 4 2 33.3% 9.9 Derek Carr 67 17 609 2 2 25.4% 9.1 Zach Mettenberger 27 9 394 3 2 33.3% 14.6 Football Outsiders Game Charting Project

Derek Carr did a lot of dinking and dunking for the Raiders, but he also connected on enough deep passes to prove that there will be much more to his game than tosses into the flats. It will be exciting to see what he does with Amari Cooper and Michael Crabtree as his receivers.

Teddy Bridgewater is supposed to have a noodle arm (or something like that; by the end of the draft cycle last year it was shocking to learn that he could walk, talk and use dining utensils) but produced league-average deep statistics for three-quarters of a season's work.

Blake Bortles, like the team around him, was messy but not hopeless.

Zach Mettenberger has a great arm and uncorked some great deep passes in limited action. It's a small sample size, but Mettenberger's stat line meshes with his scouting report, so look for capable deep passing production if we ever see him again.

The Crossroads Quarterbacks

Every quarterback we have seen so far has an uncontested starting job, so it's not surprising that the only truly weak deep passing numbers have come from quarterbacks who do other things (run, avoid turnovers, manage games, win Super Bowls) exceptionally well. What about the failed prospects struggling to earn one last chance? What about recently traded quarterbacks with something to prove to new teams? There is no way their deep passing stats fall into line with the Hall of Famers, established starters and rising stars, right?

As it turns out, the deep passing production for quarterbacks at the crossroads is all over the place. (Sam Bradford's 2012 statistics were used, since he had no 2014 stats but is too interesting to exclude.)

Deep Passing Stats: The Crossroads QBs Quarterback Att Comp Yards TD INT Comp% Yards/Att Sam Bradford 89 29 981 6 6 32.6% 11.0 Kirk Cousins 35 12 467 4 6 34.3% 13.3 Nick Foles 103 37 1272 17 7 35.9% 12.4 Mike Glennon 81 33 1138 9 4 40.7% 14.0 Robert Griffin III 71 18 683 4 3 25.4% 9.6 EJ Manuel 55 15 506 4 3 27.3% 9.2 Geno Smith 109 37 1249 9 15 33.9% 11.5 Football Outsiders Game Charting Project

Nick Foles' deep passing numbers are outstanding. He was amazing in his breakout 2013 season, with 10 deep touchdowns to just one interception in less than a full season. He was still close to league average for his playing time last season, though with a high interception rate. Foles has a very good arm.

So does Sam Bradford, who was a league-average deep passer in 2012, when he and Chris Givens looked like an emerging home run combination, and then was awful in a half-season's work in 2013, when the Rams gave up trying to throw more than three yards downfield. This season will tell us a lot about how much impact Chip Kelly's offense has on a quarterback's ability to connect with open receivers downfield.

Wilfredo Lee/Associated Press

Geno Smith has thrown more deep interceptions than any quarterback in the NFL over the last two years, despite the fact that most established starters threw 20 to 40 more deep passes than he did. That said, Smith's completion rate on deep passes is average, and he has had enough success as a downfield thrower to offer some hope for development.

The same cannot really be said of Robert Griffin III, who has given up throwing downfield unless DeSean Jackson is open by 10 yards, or EJ Manuel, whose quarterback career has been held back by his inability to throw footballs very well. Griffin's deep numbers were good as a rookie in 2012 (18-of-42, 626 yards, seven touchdowns, two interceptions), and he left college with tremendous arm skills, so there still might be a fine deep passer beneath the ticks, quirks and mistakes.

Kirk Cousins looks like a good deep passer when he first takes over a starting job, then just starts throwing interceptions in bunches.

Mike Glennon's numbers are excellent for a guy coaches would move mountains to bench. Glennon's arm has never been the problem; it's his tendency to get rattled in the pocket that gets him into trouble. He is the kind of quarterback who would look very different in a better situation; as a backup-for-hire behind a top veteran, he could grow into a fine spot starter.

The Journeymen

You thought we were scraping the bottom of the barrel with that last group, but this turns out to be a pretty deep barrel. Here's a sampling of the veteran backups, spot starters and "bridge" quarterbacks who have received significant playing time in the last two years:

Deep Passing Stats: The Journeymen Quarterback Att Comp Yards TD INT Comp% Yards/Att Matt Cassel 43 16 475 3 5 37.2% 11.0 Ryan Fitzpatrick 79 31 1158 9 7 39.2% 14.7 Brian Hoyer 76 30 970 3 3 39.5% 12.8 Josh McCown 69 24 849 8 2 34.8% 12.3 Kyle Orton 58 18 587 4 4 31.0% 10.1 Michael Vick 43 14 500 4 2 32.6% 11.6 Football Outsiders Game Charting Project

Veteran journeymen produce remarkably consistent deep passing statistics. It's almost as if Brian Hoyer, Ryan Fitzpatrick, Kyle Orton and Josh McCown are one guy who keeps changing his name to sign new contracts with desperate teams. (Hmm…) Their deep passing numbers help explain how these veterans stay in the league: Coaches know they can produce a reasonable facsimile of league-average production, in addition to all of that leadership/preparation/professionalism stuff.

Jeremy Brevard-USA TODAY Sports

That production can fall off the table, though, if the journeyman loses a step or a few miles per hour off his heater. Michael Vick was 3-of-17 on deep passes last year; Matt Cassel was 0-of-5 with two interceptions.

Watch the film and you can see how tenuous the deep production of these journeymen really is. Everything must break right for them: Hoyer needs the play-action game to set things up, Fitzpatrick needs to scramble the defense to distraction, McCown needs Mike Evans and Vincent Jackson to jump and stretch like rubber men, and so on.

We shouldn't get too high or too low on any of these journeymen. Their sample sizes are small, and they are often thrust into situations that skew their stats. Bad supporting casts can make the numbers look bad, but lots of fourth-quarter passes in blowout losses can also make the numbers look good. The relatively high completion rates on this list are probably a result of these canny veterans only taking the downfield shots they think they can make, even if their teams could really use a little more.

The Rankings

Now that we have seen the data, let's rank the quarterbacks. These rankings are based on each quarterback's completions per game, completion percentage, yards per attempt, touchdown rate and interception rate, plus some dead reckoning guesses about supporting casts and whether each quarterback is fading or developing.

Ted S. Warren/Associated Press

1. Aaron Rodgers: Rodgers blew the field away.

2. Ben Roethlisberger: Big Ben has more attempts in the past two seasons than any other quarterback, and his rate stats may suffer as a result. He tries to fire more deep passes into tight windows than others because he can. That shouldn't be held against him.

3. Peyton Manning: This feels like a controversial choice, but it's hard to argue with a 43.2 percent completion rate on deep passes, with a rotating cast of receivers, from a guy who, you know, is a Hall of Famer and holds most of the league's passing records. And no, the Colts playoff game is not incontrovertible evidence that Manning's arm is completely shot.

4. Drew Brees: Brees has more impressive raw stats than Roethlisberger. Put Big Ben in a dome and Brees in the AFC North, and the results would probably be very different. That said, there's no shame in being fourth on this list.

5. Jay Cutler: Another controversial selection that should not be. It's not like this guy is in the league for his sparkling personality.

6. Philip Rivers: The best quarterback ever to be consistently left off lists of best quarterbacks in various categories.

7. Russell Wilson: Rising fast. Wilson might rank third or fourth in 30-plus-yard passes but needs more clubs in his bag on 20- to 25-yarders. Consider Jimmy Graham a top-of-the-line 3-iron.

8. Andrew Luck: Could shoot up the charts now that his receiving corps is an Olympic relay team. The stats really suggest that deep passing is a veteran's game, with touch and timing trumping talent on many of the trickier throws.

9. Tony Romo: Consistent and dependable in this area. I would make a golf club analogy for Romo, but I don't want to rub it in for the poor guy.

10. Nick Foles: The raw numbers suggest that Foles is one of the best in the league at deep passing: He does it well, and he does it often. Slotting Matt Ryan here would be a safer choice, but until we discover just how much of Foles' success was caused by Chip Kelly's Special Culture Sauce, he needs to be included here.

And now, the worst deep passers:

5. Cam Newton: Too talented, and now far too well paid, to rank this low.

4. Ryan Tannehill: The flesh is willing to throw deep, but the spirit often looks weak.

3. Robert Griffin III: Like a Ferrari that was wrecked twice, never had the oil changed and was left outside during a winter in Siberia.

2. EJ Manuel: Would rank dead last, but there is still a chance he will improve, as opposed to the next guy.

1. Alex Smith: Make sure you take some time off before training camp, Jamaal Charles.

Mike Tanier covers the NFL for Bleacher Report.