Prior to the infamous 2013 class, conventional wisdom held that offensive tackles were the safest investments in the first round of NFL drafts.
That's no longer the case.
Left tackles, in particular, have fallen on hard times since inspiring Michael Lewis' best-seller-turned-blockbuster The Blind Side.
So what is behind the stagnant development of early-round offensive tackles over the past half-decade?
For starters, defensive-line play has gained ground on offensive lines since the CBA eliminated contact in offseason practices and restricted teams to 14 fully-padded practices per regular season.
"They're not getting any better because they don't ever get to practice football," Cardinals coach Bruce Arians explained, via the Indianapolis Star's Stephen Holder. "Since we've made the rule changes, the quality of the athlete has gone way up, and the quality of the football has gone way down. ... When we draft them, they just go through the entire spring without pads just doing stupid a-- drills that don't get them any better."
The curtailed practice schedule has been exacerbated by the growing chasm between the NCAA and pro game, with spread offenses dominating the college ranks.
College linemen typically split wide with more space between the tackles and guards and fewer defenders in the box. One of the byproducts of the uptempo spread offense is less time between plays for college pass rushers settle in and think about moves and countermoves -- as NFL Films senior producer Greg Cosell recently outlined on Yahoo! Sports Radio's The Shutdown Podcast.
When tackles get to the NFL, they have to adjust to a three-point stance, a quarterback's five- or seven-step drop, a tighter line of scrimmage, high-octane pass rushers with full arsenals of moves and countermoves, exotic defensive schemes and speedy linebackers and safeties coming on blitzes.
Arians drafted Florida star D.J. Humphries last offseason, with the full understanding that the first-round tackle would require a red-shirt season.
"So many of those guys never get in a three-point stance," Arians said at the NFL Scouting Combine in February. "... It's fundamentals that we're going back now and have to teach. We never had to teach it before. Great athletes. The athletes are much, much better, but the fundamentals are worse than they've ever been."
It's not that tackles arrive at the next level devoid of fundamentals. It's that the fundamentals in college have diverged from the NFL's fundamentals.
The same is true for other positions. Spread quarterbacks have lacked NFL staying power. Spread running games have contributed to the devaluation of the tailback position. Spread wide receivers too often arrive on the scene armed with just a handful of routes, specializing in bubble screens and slants.
The skill-position players often boast enough pure talent to get by on instincts while learning the pro game. It's a different story on the offensive line, where the best players are also the most effective technicians.
Colts general manager Ryan Grigson has a mandate to fix his leaky pass protection this week after drafting six offensive linemen since 2012.
"People don't like to say it," Grigson acknowledged, per Holder, "but there is some guessing going on in this thing, some hypothetical evaluation and imagination."
Pro Football Focus illustrates that challenge, pointing out that Notre Dame's Ronnie Stanley and Ole Miss' Laremy Tunsil -- this year's consensus top two tackle prospects -- combined to protect on a seven-step drop 42 times last season. Pro tackles average more than 120 seven-step drops per year.
That doesn't mean Tunsil, Stanley and Michigan State's Jack Conklin are destined to become first-round busts. It does mean they will likely need extra time to master the necessary fundamentals and technique -- just as Humphries did last season under Arians' tutelage.