The NFL draft has an enormous carbon footprint. It's impossible to count how many flights are taken, cars are rented and rib-eyes are consumed as the league's 32 teams of personnel experts crisscross the country to weigh, measure and size up prospects.

Then there's the hot-air factor.

How many hours of TV and talk-radio programming get spent breaking down the resulting evaluations is anybody's guess. But if half as much analysis were devoted to fixing society's ills as has been done dissecting Jameis Winston's moral fiber and Marcus Mariota's capacity for changing plays at the line of scrimmage, the world surely would be a better place.

What's most astonishing, though, is how much of a crapshoot the process remains.

"Any time you go to draft, you're predicting the future," St. Louis Rams general manager Les Snead. "(But) each player's DNA is different."

For every J.J. Watt or Patrick Peterson or A.J. Green, there's a Trent Richardson, a Derrick Sherrod or a Jonathan Baldwin. All were first-round picks in 2011, each having been judged to be among the best-of-the-best college prospects by the people burning all that jet fuel and regular unleaded while keeping the slaughterhouses humming.

The first three proved worthy of the time, effort and trouble, establishing themselves as instant NFL assets and, now, perennial Pro Bowlers who could finish their careers as Hall-of-Famers-in-waiting. But the latter trio will get inside only if they can afford the price of admission.

Sherrod, an offensive lineman, suffered a broken leg as a rookie and wound up playing only 263 snaps over three seasons for Green Bay before being let go. Watkins, another can't-miss offensive lineman, blocked so badly for Philadelphia that some blame him for coach Andy Reid's firing. Richardson, the couldn't-miss running back, gained only 1,055 yards in two seasons in Cleveland before the Browns cut their losses and traded him to Indianapolis, where he also languished.

The Houston Chronicle's in-depth draft study went back to the 2011 draft because most NFL executives believe it takes that long to fairly assess the quality of a class.

"There's a reason why we put free agency four years out," said Mike Maccagnan, the Texans' former director of college scouting who will be going through his first draft as the New York Jets' general manager. "At that point, these guys have become what they've become. A year out, you have an idea, but after two or three years you have a much better idea of (the quality of a draft class)."

Pro Bowlers the exception

The research shows that no team got it right across the board.

More Information Four-year plan A look at how the past four draft classes for 2011 first-round pick J.J. Watt, below, and the Texans have fared: 35Draft picks(NFL rank: T-8th) 751Games played (NFL rank: 5th) 21.5Games played per pick(NFL rank: 10th) 27,048Snaps played(NFL rank: 3rd) 773Snaps per pick(NFL rank: 10th) First round: 7 p.m. Thursday at Chicago's Auditorium Theatre.TV: ESPN and NFL Network. About the project The Chronicle's Brian T. Smith and Dale Robertson spent more than 100 hours on research and analysis to determine how the Texans and the NFL's 31 other teams have fared in the 2011-14 drafts. Data for this project was limited to a four-year period, matching the length of rookie contracts. A focus was placed on controlled stats that mirrored on-field production. Games played show that a selection was talented enough to make a 53-man roster, then continually take the field. Snap counts mirror talent, production and longevity on good teams while revealing the limitations of bad ones.

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Nobody even came particularly close, certainly not four years running. The 1,017 players selected over the past four springs collectively made appearances in just over half the games their teams have played. Fewer than a quarter (231) averaged as many as 500 snaps per season with their original franchise. Barely 3 percent (31) averaged more than 1,000. Only 13 percent (128) played in every game.

Pro Bowlers? Thirty-nine were honored at least once. Cincinnati receiver A.J. Green and Arizona cornerback Patrick Peterson are the only four-time Pro-Bowlers. Texans defensive end Watt, already twice named the NFL Defensive Player of the Year, is the lone player to be chosen as either the top offensive or defensive player.

Indianapolis quarterback Andrew Luck is the lone three-time Pro Bowler from the 2012 class. Chicago offensive tackle Kyle Long is the only 2013 draftee to go 2-for-2. The 2014 class produced three rookie Pro Bowlers - Dallas guard Zack Martin, New York Giants receiver Odell Beckham and Cincinnati linebacker C.J. Mosley.

At the opposite end of the contribution spectrum, over half (129) of all drafted players got on the field for fewer than 100 snaps.

Still, the draft seems to capture the public's fancy more and more every year. This drawn-out process, a cases study of paralysis by analysis if ever there was one, has become a season unto itself, starting with the combine in mid-February, continuing through the myriad "pro days" and finally the 72-hour selection process.

Despite the sound and the fury, it's a flat-out folly to think of the draft as the be-all-end-all factor in a franchise's ultimate success. In fact, many of the most "productive" drafts, reasonably defined by how much playing time the draftees ultimately receive, belonged to the worst teams.

Consider the extremes represented by Cleveland and New England. Thirty players averaged an NFL-high 993 snaps as Browns. But Cleveland's four-year total of 20 victories ranks fourth from the bottom. The Patriots' 32 choices, in turn, averaged more than 200 snaps fewer when they were winning a league-best 49 games, plus Super Bowl XLIX.

49ers a classic example

Yet imagine how bad Tampa Bay (17 wins, 868 snaps per player) and Jacksonville (14 wins, 817 snaps per player) might have been if they hadn't found able bodies capable of plugging holes while learning on the fly. Imagine if they had come up as empty-handed as San Francisco and New Orleans.

The 49ers had the most picks (40), but they averaged a league-worst 318 snaps. They chose pretty well in 2011, landing pass-rusher Aldon Smith and quarterback Colin Kaepernick in the first two rounds, before advancing to the Super Bowl in 2012. But they've been a draft-weekend train wreck since with only free safety Eric Reid, their No. 1 in 2013, having established himself as a reliable every-down player.

Of the seven players San Francisco drafted in 2012, only three got on the field as 49ers, combining for fewer than 500 snaps and playing in barely 12 percent of the 336 possible games. Even the Texans' mostly abysmal 2013 draft - just three of the nine picks have seen any playing time - appears marginally better with a game-participation rate of 33 percent. It's reasonable to argue that the Niners' fall from the playoffs last season largely can be hung on the annually diminishing draft returns.

Green Bay, meanwhile, offers an intriguing contrast. Although its 38 picks have averaged a third-worst 519 snaps, the Packers have won 46 games, second only to the Patriots, and made the playoffs every January. The difference? Green Bay was 10-6 in 2010 and had an established superstar quarterback in Aaron Rodgers. San Francisco was 6-10 in 2010 and hadn't yet found the guy, albeit Kaepernick was briefly.

"Some of it's physical (strength)," Minnesota GM Rick Spielman said when asked about the transition from college to pro ball. But Spielman believes a more important variable is a player's maturity.

"It's different in the NFL from just relying on your skill set," he said. "There are (so many) nuances of the game they have to learn. The speed of the game is much faster. Some of the guys get it early, but for some it takes a couple years. We try to look at a three-year window. We grade them every year but want to continue to see them make progress."

For the fans' amusement

By that definition, Spielman can't be too happy with the Vikings' 2011 class. None of the 10 picks, who combined to play in only 35 percent of the games, held down larger roles in their fourth season than they had in their rookie year. Most conspicuously, by 2014 Minnesota already had moved on from 2011 No. 1 pick quarterback Christian Ponder.

There have been 128 players taken in the first round the last four springs. Two-thirds have averaged at least 500 snaps per season with the team that selected them. Also, 20 have gone to at least one Pro Bowl. However, considering that every player drafted in the first round is presumed to have Pro Bowl potential, 108 "misses" is a large number.

Hence, caring too deeply about how, or whom, a team drafts is largely a fool's errand, practically guaranteeing unhappiness and frustration. So the Rams' Snead suggested keeping one's perspective as draft day approaches.

"A little bit of it (is about) entertainment," he said. "It's just fun for the fans to stay involved."

Brian T. Smith contributed to this report.