Is This the End of the Franchise Left Tackle?

What do Von Miller, J.J. Watt, Justin Houston and Khalil Mack have in common? You can't protect your quarterback from them with an elite left tackle.

Not just because they're four of the most feared pass-rushers in the NFL, but because they line up on the other side of the field. Three of these explosive sack artists rushed the passer from the offense's right side more often than its left in 2015, per Pro Football Focus, and ESPN.com's Tania Ganguli showed Watt did the same in the 2014 season.

For decades, the left tackle has been the only obstacle between a team's most critical player and its opponent's most dangerous player. But offenses and defenses always adapt and evolve, changing in response to the trends on the other side of the ball.

For years, defenses have moved away from building a pass rush around one primary rusher and toward symmetrical, rotational schemes that involve sending pressure through every gap in the line. Until now, the way teams scout, draft and sign offensive tackles hasn't evolved to account for this.

In 2015, NFL teams committed an average of $5.4 million in cap dollars to left tackles, per Spotrac, and $2.8 million to right tackles—but in a world where the pressure is coming just as often from the right as the left, this doesn't make any sense.

The highest-paid right tackle in the NFL is the Philadelphia Eagles' Lane Johnson. He just signed a five-year extension this January with an average annual value of nearly $11.3 million, per Spotrac. Even that deal, though, reflects Johnson's status as Jason Peters' heir apparent—likely to move to the left just a season or two into the deal.

No, the going rate for top right tackles is still south of $7 million per year, as reflected in the contracts just signed by Mitchell Schwartz and Jermey Parnell, both valued just under Bryan Bulaga's second-highest $6.75 million-per-year deal.

Among left tackles, that top-of-the-market pay rate for right tackles slots between 16th (King Dunlap) and 17th (Ryan Clady).

It's not that NFL teams don't know they're passing far, far more often than they used to, or that pass rush is increasingly being generated by athletic freaks who line up all over. It's just that until now, they've been adapting the wrong way.

Teams have been drafting more and more tackles higher and higher over the past eight years. Using the standard draft trade value chart, teams spent 50,625 "points" on 38 first-round offensive tackles from 2008 to 2015. That's almost twice as much as the 28,480 points spent on 21 first-round tackles in the previous eight years:

Ty Schalter/Bleacher Report

But simply drafting offensive tackles higher hasn't made them any better.

The much-hyped trend toward lean, agile left tackles has resulted in a string of high-profile strugglers, topped by 2013 No. 1 overall pick Eric Fisher. Whether it's been performance, injury or both, teams have gotten little quality pass protection out of players like Fisher, Matt Kalil and Jason Smith.

Pro Football Focus graded Fisher 76th out of 84 qualifying tackles in 2014 and negative in both pass-blocking and overall grades in 2015. After a stellar rookie year, Kalil has turned in three straight years with negative Pro Football Focus overall and pass-blocking grades.

Smith, the 2009 No. 2 overall pick, started only his second season (at right tackle, no less); the then-St. Louis Rams gave up on him after the 2011 season, and he hasn't made a roster since 2012.

It's not just the skinny guys, either: "Safe" all-arounders have struggled, too. In 2014, I was convinced Jake Matthews was a great value at No. 6 overall; he was PFF's worst-graded tackle that year. Greg Robinson was just slots above Matthews in 2014, and in 2015, he was ranked 73rd overall out of 76 tackles. 

Athletically limited brawlers like Ereck Flowers still struggle mightily on the left; the 2015 No. 9 overall pick received a minus-40.7 pass-blocking grade from PFF his rookie season—the worst pass-protection grade PFF has ever recorded. The Cardinals drafted D.J. Humphries in the first round last year, and he couldn't even dress for a single game.

Mark J. Rebilas-USA TODAY Sports

The draft-industrial complex, as I like to call it, continues to evaluate offensive tackles as if left tackles must be athletic pass protectors and right tackles massive run-blockers. But at every other position group, the traditional asymmetries of the game are disappearing.

Most teams line up in shotgun more than 50 percent of the time and overwhelmingly pass when they do, so there really isn't a blind side anymore. Tight ends are slimmer, faster, move all around the formation and do far less in-line blocking, so there really isn't a strong side, either.

Those changes are mirrored on the defense: All linebackers need to be able to cover, usually in the context of a nickel defense, and there certainly isn't room on the field for a so-called extra linebacker at strong safety.

So when it comes to offensive tackles, why are NFL teams drafting like it's 1999?

Maybe 2016 is the year it all changes. It's a copycat league, after all, and the Denver Broncos not only won the Super Bowl without their high-priced left tackle, Clady, but traded him away for peanuts afterward. The cautionary tales of Fisher, Flowers and Humphries may be shocking draft boards back into reality, too.

As wise Bleacher Report readers enter mock draft contests or debate with friends over who'll be their team's next rookie hope, they'll know: Not every big tackle is Orlando Pace, and a "right tackle only" is probably a guard.

They can only hope their team knows, too.