Quenton Nelson looks exactly like a franchise-cornerstone left tackle: Standing 6 foot 5, 325 pounds, Nelson is “built like a bank safe” and blessed with the athleticism and aggressiveness to be a perennial All-Pro. The quarterback’s protector is often called the second-most-important offensive position, so it’s no wonder that Nelson’s in the mix to be the first non-quarterback to be picked in this year’s draft.

But one thing does separate Nelson from other highly coveted tackles on draft day: He isn’t a tackle. He’s a guard.

How players at one position in the NFL’s otherwise-anonymous quintet of trench warriors became some of American sports’ most-prized athletes is a story so well-known it was turned into a best-selling book, and even a movie: The uniquely gifted protectors of “The Blind Side” emerged in the 1990s to stop the pass-rushing outside linebackers of the 1980s, like eight-time All-Pro Lawrence Taylor.

For years afterward, teams trying to land the next Orlando Pace or Walter Jones had no qualms about throwing high draft picks at top tackles. Even less-than-perfect tackle prospects like Michigan’s Jake Long and Central Michigan’s Eric Fisher were deemed “safe” picks at No. 1 overall — because unlike quarterbacks, who are unlikely to play another position well, if those tackles fail to establish themselves as quality starters, teams have the option of kicking them inside to guard.

As recently as 2012, guards were still afterthoughts, not worthy of the draft-value (and contract) investment that comes with a high first-round selection. Outstanding guard prospect David DeCastro, whom many evaluators deemed worthy of at least a top-10 pick, didn’t come off the board until No. 24 that year.

In the 32-team era, 62 tackles have been drafted in the first round compared to just 14 guards. On average, those tackles were taken with the 14th pick, while the average guard went between 23 and 24. In fact, after “The Blind Side” was released in September 2006, NFL teams went on a four-year tackle binge, drafting 19 first-round tackles compared to just three centers and two guards.

Last season, though, the market for elite tackles seemed to dry up. Only two — Garett Bolles and Ryan Ramczyk — went in the first round, and both were picked in the back end of the round (20 and 32 respectively). After Alabama’s Cam Robinson was taken with the second pick of the second round, which was lower than most expected, no tackles were taken until pick No. 85. To get a sense of how high in the draft tackles have tended to go over time, we can quantify pick position using Jimmy Johnson’s draft-pick value chart, which assigns a point value to every pick in the draft based solely on how early the pick is, not on which player is taken. Last year, the picks used on tackles in rounds one and two were worth a total of 2000 points, the lowest sum since at least 1994. By comparison, the picks used on the six tackles taken in the first two rounds in 2013 were worth more than 10,000 points.

The trend of devaluing tackles seems certain to continue in the 2018 NFL draft. After Nelson, tackle Mike McGlinchey (average mock draft position: 22.2) is the next offensive lineman projected to go. But then it’s a run of interior linemen: Center James Daniels (28.5) and guards Isaiah Wynn (28.8) and Will Hernandez (28.9) are all set to be drafted ahead of the only other tackle who’s projected to be taken on the draft’s first night, Kolton Miller (31.2).

If Miller doesn’t make it into the first round, it’ll be the first time that fewer than two tackles have been drafted in any first round since “The Blind Side” was released, and it would match the 2005-2006 nadir for high-pick tackles — only three tackles were taken in the first round in each of those two back-to-back draft classes.

It’s not like NFL teams suddenly decided that the offensive line isn’t important, it’s more that the value pendulum is shifting away from left tackle. If Nelson goes as high as he’s expected to, he’ll be the third guard picked in the top 10 in the last six seasons (the fourth if you count Washington’s Brandon Scherff, who was drafted as a tackle but has since become a Pro Bowl guard ). Before Chance Warmack and Jonathan Cooper went in the top 10 in 2013, no guard had been picked that high in a dozen years.

But it’s not just draft capital that teams are investing in a previously neglected position.

This spring, All-Pro guard Andrew Norwell signed a five-year, $66.5 million unrestricted free-agency deal that briefly made him the NFL’s highest-paid offensive lineman. Though former New England Patriots left tackle Nate Solder’s four-year, $62 million contract with the New York Giants topped Norwell’s $13.3 million average annual value, Norwell remains No. 2.

In 2016, the five biggest free-agency deals given to offensive linemen went to left tackles. In 2017, half of the eight offensive-line contracts worth at least $10 million per year went to left tackles — but the other half went to three guards and a center. In 2018, Solder’s was the only one of the top six offensive-line deals that did not go to a guard or center.

So why the sudden change? For starters, the evolution of the left tackle was a response to a defensive revolution that’s been over for a long time; Taylor’s 10-season Pro Bowl streak ended 27 years ago. From Dick LeBeau’s zone blitzes to Jim Johnson’s and Jim Schwartz’s aggressive 4-3s, Wade Phillips’s one-gap 3-4 schemes to Bill Belichick and Matt Patricia’s hybrid/multiple fronts attack, defensive coordinators have as many different ways to send pass rushers at quarterbacks as there are gaps between offensive linemen.

According to ESPN Stats & Information Group, 36 percent of the 1,082.5 sacks by front-seven players in 2017 were registered by a player lined up at right defensive end or right outside linebacker. That means even a Hall of Fame left tackle can’t possibly help with at least two-thirds of the pressure that defenses are generating.

Then there’s the fact that quarterbacks don’t really have a “blind side” anymore. The heavy use of shotgun formation in today’s NFL allows quarterbacks to keep the whole defense in front of them. According to ESPN Stats & Info, just 13,319 of 32,436 offensive plays (41 percent) were run from under center in 2017– and of those, a quarterback dropped back to pass on just 4,201 plays (13 percent of all offensive plays).

The average left tackle, then, will only be called upon to keep his quarterback clean during a traditional dropback about 1/8th of the time he’s on the field.

But don’t tell Nelson, Wynn, Hernandez or any of the other guards set to be drafted this weekend that the value of offensive linemen has crashed. They’re about to prove that the NFL has finally figured out that anyone who can get keep a pass-rusher from getting to a quarterback is worth an awful lot — regardless of where he’s positioned on the line.