Every NFL draft seems to have at least one exception to a widely held, well-known rule lurking inside its player pool. Russell Wilson, as an example, was the exception to the rule that you don't draft short quarterbacks. And when the Titans bucked history to take Alcorn State quarterback Steve McNair out of Division I-AA with the third overall pick in 1995, that move worked out, too. At a certain point, it seems, all rules must be tested.

This year's exception to the rule is Ezekiel Elliott, the athletic, powerful, short-on-weaknesses running back who has drawn comparisons to Adrian Peterson -- if not in running style, then in overall excellence at the position. Running backs aren't supposed to be taken at the top of the first round, the current rule holds, but Elliott's versatility and supreme talent suggest that he's worth ignoring the rules altogether. That's why teams like the Cowboys are rumored to be interested in him as a top-five selection.

If Elliott turns out to be the next Peterson or Todd Gurley, the Cowboys -- or whoever takes Elliott -- will consider him to be a worthy return on a high first-round pick. The downside, of course, is that we know Trent Richardson was considered to be every bit as good of a prospect as Peterson, and yet he ended up as a colossal misstep for the Browns and Colts. Richardson, thought to be an exception, was the reason the rule existed in the first place.

Beyond Elliott, Peterson and Richardson, though, the whole idea of treating players at a given position as far better prospects than their positional brethren got me wondering:

How often do these sorts of unexpectedly high-drafted talents work out?

Should organizations be more aggressive in going after the guy who is clearly a top talent at a given position without really worrying about how the league typically values players at that spot in the lineup?

Or should they trust the league's judgment and wait until history suggests it's OK to go after a player at a position like running back or kicker?

To gain some insight into how those players have turned out, I went back through the past 20 years of drafts and sorted out players by the position they were expected to play when they were drafted. To the best of my ability, I sifted through the player pool to include 4-3 defensive ends and 3-4 outside linebackers as one group of edge-rushers while identifying other linebackers as cover/interior linebackers.

After sorting through all the players, I identified the top-drafted player at each positional group during those past 20 drafts, and then used the median of those 20 draft slots to identify where the top-ranked player at a given position in a typical draft would likely come off the board. As an example, the median draft position for the first center taken over the past 20 years is the 44th selection. The first center taken in 2015 was Cameron Erving, who was selected by the Browns with the 19th pick in the first round. Erving, then, was 25 picks ahead of our expectation of where the top-ranked center is likely to go in a given draft.

Let's go position by position, identify the most notable outliers for top selections at each spot over the past 20 years and see how their professional careers turned out in preparation for Elliott and the rest of the class of 2016:

Quarterback

Median Top Draft Position: 1st overall pick

Highest-Drafted Outliers: (13 of the past 20 first overall picks are quarterbacks)

This analysis doesn't offer much insight into quarterbacks, given that the best passer in a given draft class more often than not comes off the board with the first overall pick. That doesn't seem likely to be the case for Carson Wentz or Jared Goff this year, but they're still all-but-assured to find their new homes during the first half of the first round. Fourteen of the past 15 drafts have had at least one quarterback taken amidst the first three picks, with the 2013 draft (featuring EJ Manuel leading off a dismal crop of quarterbacks at 16) as the lone exception. It's not surprising: Teams selecting at the top of the draft are often desperate for a quarterback upgrade, and even if there's not a great passer out there, it's easy to look at a promising college passer as a life preserver.

Running Back

Median Top Draft Position: 8th overall pick

Highest-Drafted Outliers: Ronnie Brown (2005, 2nd overall pick, +6 picks vs. expectation); Reggie Bush (2006, 2nd overall pick, +6); Trent Richardson (2012, 3rd overall pick, +5)

Trent Richardson was considered a potential star NFL running back, but instead has reinforced the worst suspicions about RBs. John Korduner/Icon SMI

Well, that's not promising. It seems surprising that the typical top-ranked running back is still a top-10 selection, but that's not an artifact of the older drafts in that 20-year period; even if we just look at the 10 most recent drafts, the median top running back came off the board with the 10th selection. The real outlier is on the opposite side -- in 2014, when the first running back to come off the board was Bishop Sankey at No. 54, 46 picks after our expectations of when the top-ranked back would appear. (In a related note, Devonta Freeman aside, the backs from that class haven't exactly lit the world on fire.)

Neither did the three highest-drafted backs of the past 20 years. Ronnie Brown joined Cedric Benson (4th) and Cadillac Williams (5th) in what was one of the most expensive running back classes in terms of draft capital in league history, but the best backs from that class weren't taken until much later, when Frank Gore (65th) and Darren Sproles (130th) went to the 49ers and Chargers, respectively.

It was controversial at the time when the Houston Texans passed on Reggie Bush to take Mario Williams with the first overall pick, but history has shown them to be right, given Bush's inconsistent professional career. And Richardson has been one of the least productive running backs in recent league history. It's not impossible to think that he might be able to turn around his career in much the same way that former college teammate Mark Ingram was able to carve out a role in New Orleans, but time is against the former sure thing.

Wide Receiver

Median Top Draft Position: 6th overall pick

Highest-Drafted Outliers: Keyshawn Johnson (1997, first overall pick, +5); Charles Rogers (2003, second overall pick, +4); Calvin Johnson (2007, second overall pick, +4)

An interesting group of wideouts are atop the leaderboard here. Keyshawn Johnson had a solid, 11-year professional career without ever producing a dominant season; Johnson made three Pro Bowls without ever making an All-Pro team, and had only one season in which he ranked among the top 10 receivers in fantasy football, which (in this case) is a useful marker of production. Jets fans still look back and wonder what would have been if Peyton Manning had come out of Tennessee one year earlier, although they did get two first-round picks for Johnson when the Jets traded him to Tampa Bay in 2000.

The two Detroit selections at the top of the draft are more obvious. Charles Rogers was a colossal bust, a physical specimen with a terrible habit of landing directly on his collarbone. The Lions took him one pick ahead of Andre Johnson, which must make Detroit fans feel as if they just landed directly on their collective collarbone. Four years later, Matt Millen made a far more successful pick when he drafted Calvin Johnson, but even the recently retired Megatron makes Lions fans feel sad these days. The two third-overall picks at wideout also sprint in opposite directions: Larry Fitzgerald (2004) and Braylon Edwards (2005).

Tight End

Median Top Draft Position: 23rd overall selection Highest-Drafted Outliers: Kellen Winslow (2004, sixth overall pick, +17); Vernon Davis (2006, sixth overall pick, +17); Rickey Dudley (1996, ninth overall pick, +14)

Just behind this group is 2014 Lions first-rounder Eric Ebron, also known as the guy ex-GM Martin Mayhew chose ahead of Odell Beckham Jr. and Aaron Donald. Let's leave poor Detroit alone for a while. Here, we have the most dramatic gap between typical selection and top selection, which is useful: We can really see teams going out of their way to target players well ahead of where the league might typically value the best player at a given position.

And again, truthfully, results are mixed at best. Kellen Winslow's athleticism was sapped by the fractured fibula he suffered as a rookie and torn ACL he subsequently suffered in a motorcycle accident before what would have been his second season. He ended up making one Pro Bowl while toiling for mostly terrible football teams. Vernon Davis overcame attitude concerns early in his career to emerge as a dominant blocker and above-average red zone weapon, making two Pro Bowls when his touchdown totals spiked to double digits in 2009 and 2013. Davis was never the sort of dominant receiver up and down the field, though, failing to make it to 1,000 receiving yards in even a single professional season. Rickey Dudley was Davis without the dominant blocking.

Offensive Tackle

Median Top Draft Position: 4th overall pick

Highest-Drafted Outliers: Orlando Pace (1997, first overall pick, +3); Jake Long (2008, first overall pick, +3); Eric Fisher (2013, first overall pick, +3)

He's not a bust, but Eric Fisher hasn't lived up to the potential we associate with a typical top prospect at his position. Brad Penner/USA TODAY Sports

We're still waiting for a position in which the outliers all turned out well. This isn't it. Orlando Pace is a newly inducted and deserving Hall of Famer, but that's not the case with the other two tackles. Long had a promising start to his career, making four consecutive Pro Bowls, before myriad injuries reduced him to a shell of his former self. Eric Fisher has been a disappointment for the Chiefs, although he seemed to finally show signs of life as the season went along in 2015. The nicest thing you can say is that the Chiefs at least made the right choice in taking Fisher over Luke Joeckel, who has been even more disappointing for the Jaguars.

Even scarier: The tackles who went off the board with the second overall pick over the past 20 drafts are even worse. There are two failed tackles who only found success after converting to guard (Robert Gallery and Leonard Davis), a failed tackle who converted to a new career (Jason Smith) and a tackle who has committed 24 penalties in two seasons (Greg Robinson). Run away, Laremy Tunsil!

Guard

Median Top Draft Position: 22nd overall pick

Highest-Drafted Outliers: Jonathan Cooper (2013, seventh overall pick, +15); Chris Naeole (1997, 10th overall pick, +12); Branden Albert (2008, 15th overall pick, +7); Mike Pouncey (2011, 15th overall pick, +7)

Branden Albert and Mike Pouncey were both players who mostly lined up at guard in college, although they've made their hay in the pros playing other positions. Albert has been a left tackle for the Chiefs and Dolphins, while Pouncey has spent the vast majority of his professional career at center. Get rid of them and you're looking at former Eagles star Shawn Andrews and current Cowboys guard Zack Martin, who was a college offensive tackle.

The two guys remaining weren't dominant players. Chris Naeole was a solid veteran out of Colorado who enjoyed an 11-year career with the Jaguars and Saints without ever making a Pro Bowl. Jonathan Cooper's career, meanwhile, has gotten off to a disastrous start, with injuries and disappointing performances, leading the Cardinals to send him to the Patriots in the Chandler Jones trade earlier this offseason.

Center

Median Top Draft Position: 44th overall pick

Highest-Drafted Outliers: Damien Woody (1999, 17th overall pick, +27); Maurkice Pouncey (2010, 18th overall pick, +26); Cameron Erving (2015, 19th overall pick, +25)

This might be the best showing of the outliers at any position so far, which is a little scary. Damien Woody bounced around and started at just about every spot on the offensive line at one point or another, moving up the traditional positional spectrum and eventually ending up at right tackle for the Jets toward the tail end of his career. He had an above-average career. Maurkice Pouncey has been excellent when healthy, but he missed 63 of 64 quarters in 2013 after getting hurt in the opener and was out injured for all of 2015. Cameron Erving was healthy as a rookie and started four games, but there were few players in football who were worse last season than Erving on a snap-by-snap basis. He'll move into the starting lineup by default after Alex Mack left for Atlanta this offseason.

Edge Rusher

Median Top Draft Position: 4th overall pick

Highest-Drafted Outliers: Courtney Brown (2000, first overall pick, +3); Mario Williams (2006, first overall pick, +3); Jadeveon Clowney (2014, first overall pick +3)

Courtney Brown is certainly a cautionary tale about the prospect of getting the best player at one position. Getty Images

A trend appears to be emerging. Courtney Brown wasn't able to stay healthy, failing to complete even a single 16-game season after his rookie campaign and finishing his six-year career with just 19 sacks. Jadeveon Clowney has already sat out 15 of 32 games as a pro after microfracture surgery on his knee and was angry after being scratched for Houston's playoff loss to Kansas City this past season. The best player of the bunch is Mario Williams, who was run out of Buffalo by cap woes and anonymous sources this offseason.

Interior Defensive Linemen

Median Top Draft Position: 8th overall pick

Highest-Drafted Outliers: Darrell Russell (1997, second overall pick, +6); Ndamukong Suh (2010, second overall pick, +6); Gerard Warren (2011, third overall pick, +5); Tyson Jackson (2009, third overall pick, +5); Marcell Dareus (2011, third overall pick, +5)

This group would be better with Gerald McCoy, taken third after Suh in 2010. (He's not included, naturally, because he wasn't the first interior lineman taken in that draft.) Russell was a dominant interior pass-rusher who failed multiple drug tests. Gerard Warren developed the nickname "Big Money" for his spending habits and never made a Pro Bowl. Tyson Jackson has been inconsistent at best as a five-technique end, disappointing the Chiefs and Falcons. Ndamukong Suh and Marcell Dareus have been very good, although they're each coming off of a disappointing 2015.

Inside Linebackers/Cover Linebackers

Median Top Draft Position: 12th overall pick

Highest-Drafted Outliers: Aaron Curry (2009, fourth overall pick, +8); A.J. Hawk (2006, fifth overall pick, +7); Rolando McClain (2010, eighth overall pick, +4)

This is sort of a weird mix of 3-4 inside linebackers and 4-3 outside linebackers, so maybe it's easier to think of it as linebackers whose primary job is not rushing the passer. Under any circumstances, it's another group of players who clearly didn't work out the way their teams expected. Aaron Curry was a dynamic playmaker in college, but his skills never translated to an NFL role, and he fell out of favor with the Pete Carroll regime before losing his job to K.J. Wright and being traded to Oakland. His career lasted only four seasons.

A.J. Hawk never lived up to that draft position in Green Bay, even if he ended up as a perfectly acceptable inside linebacker. He has managed a 10-year career without a single Pro Bowl appearance. And Rolando McClain struggled with off-field issues as a member of the Raiders before bouncing around to Baltimore and then Dallas, where he rebuilt his career with an impressive 2014 season. The most successful first-drafted linebackers were just behind these three at ninth (a group including Luke Kuechly and Brian Urlacher) and 11th (including Patrick Willis).

Cornerback

Median Top Draft Position: 8th overall pick

Highest-Drafted Outliers: Shawn Springs (1997, third overall pick, +5); Charles Woodson (1998, fourth overall pick, +4); Quentin Jammer (2002, fifth overall pick, +3); Terence Newman (2003, fifth overall pick, +3); Patrick Peterson (2011, fifth overall pick, +3)

There are no total washouts among this five-person group, which makes it the most successful positional outlier we've seen so far. You know how good Charles Woodson and Patrick Peterson have been. Shawn Springs, Quentin Jammer and Terence Newman weren't quite up to that level, but they each started for more than a decade, with Newman still going for the Vikings at age 38. Does this mean Jalen Ramsey will last forever? Probably not, but it at least makes me think that a team in the top five would be taking less of a risk by drafting a cornerback high than it might otherwise seem.

Safety

Median Top Draft Position: 17th overall pick

Highest-Drafted Outliers: Sean Taylor (2004, fifth overall pick, +12); Eric Berry (2010, fifth overall pick, +12); LaRon Landry (2007, sixth overall pick, +11)

It's incredibly unfair to pass any judgment on Sean Taylor, who was tragically murdered at the age of 24. Even if we don't include him, though, our safety list expands to include seventh overall picks Michael Huff (2006) and Mark Barron (2012), both of whom failed to deliver on expectations coming out of school. Eric Berry overcame a torn ACL and Hodgkin lymphoma to emerge as one of the best safeties in football, but Landry never developed as a player beyond an urge to lay out receivers with big hits, many of which he often missed.

Kicker

Median Top Draft Position: 119th overall pick

Highest-Drafted Outliers: Sebastian Janikowski (2000, 17th overall pick, +102); Mike Nugent (2005, 47th overall pick, +72); Nate Kaeding (2004, 65th overall pick, +54)

Fans of Roberto Aguayo rejoice! I have to admit that I suspected kickers would look particularly dismal by this sort of analysis, but this is a relatively solid group of specialists, given that Sebastian Janikowski is still playing 17 years later and Nate Kaeding was one of the more accurate kickers in league history. Janikowkski has generated 53 points of Adjusted Value, identical to fellow first-rounders Todd Heap, Ike Hilliard and Jason Campbell, which isn't bad for a kicker. Even Mike Nugent went on to have a solid professional career after failing to be particularly impressive with the Jets.

Kickers! Who knew?

Punter

Median Top Draft Position: 142th overall pick

Highest-Drafted Outliers: Bryan Anger (2012, 70th overall pick, +72); B.J. Sander (2004, 87th overall pick, +55); Brad Maynard (1997, 95th overall pick, +47)

The same success sadly didn't lend itself to punters. Brad Maynard had a long career with the Giants and Bears, so he gets extra credit for wind-related degree of difficulty, but the other two didn't live up to expectations. Bryan Anger just moved from Jacksonville to Tampa after four anonymous years with the Jaguars; perhaps unfairly, he's going to be remembered as the player Gene Smith took in the third round instead of Russell Wilson. And B.J. Sander was the anti-Packers pick; Green Bay traded up to nab him in the third round and saw him struggle mightily during his lone season with the team. The only good news is that he finished his career with a perfect completion percentage after throwing a four-yard pass as a pro.

The conclusion?

The extent of the evidence here is more ancedotal than comprehensive, but it seems to point to an increasingly obvious conclusion: It's almost always better to trade down and acquire extra picks than it is to think that you're smarter than the crowd and target a player at the top of the draft at a given position. While the players at the top of drafts are unquestionably talented, they just don't seem to succeed at a disproportionately high rate given their pedigree coming into the league. And while Elliott might look like a perfect prospect as he comes into the league, teams drafting in the top 10 are likely better off remembering what they know about running backs and shop for ball carriers in the later rounds.