Unless something bizarre happens next Thursday, Texas A&M’s Myles Garrett will become the 16th defensive player in the past 50 years to go first overall. Statistically speaking, though, there’s about a 50–50 shot that he won’t live up to the hype. Among his 15 predecessors dating back to 1967, just seven went on to make the Pro Bowl, which is a relatively low bar for a player who’s expected to be the best pro in his class. In fact, for any player chosen in the first round, the odds aren’t much better that he’ll even end up as a starter for the team that selects him.

To understate it, scouting college prospects for the NFL is hard, and evaluators get things wrong all the time. Surefire stars flame out, mid-round draft picks become All-World quarterbacks, and some players just end up in the wrong situation and never recover. So, in order to get a better idea of the challenges and conundrums that evaluators encounter, I asked a handful of them about the players they’ve missed on — and about why so many prospects don’t work out.

The hard part isn’t grading what a prospect has done in college. It’s using that performance to determine what they’re capable of in the NFL.

“You’re supposed to be looking for what the tape says they can become,” NFL.com’s Lance Zierlein told me. “The biggest mistake an evaluator can make is assuming that whoever the player is in college is who they’re going to be in the pros.”

Since he became such a different player after he went from college to the NFL, Steelers running back Le’Veon Bell was a frequently cited miss for the evaluators I spoke to.

“Bell was a little bit bigger [at Michigan State] than what he’s playing at now, and he showed a really good level of athletic ability on the field,” said former Giants, Jets, and Eagles scout Dan Hatman, who’s now director of scouting development at The Scouting Academy. “But he wanted to take everything to the outside, get in space, and hurdle people. And one of my notes was, I didn’t know if you could trust him to play in the A and the B gaps. And he’s proven me wrong on that.”

Bell has exceeded every expectation in the passing game too. The guy who caught 32 passes for 167 yards and a touchdown his junior year has developed into the standard for the new breed of hybrid running back–receivers in the NFL.

“As far as his receiving skills,” said Hatman, “you didn’t necessarily turn on the film and say, ‘Huh, we could align this guy all over the field and do all kinds of stuff with him.’ That’s the beauty of coaching. Coaches see their guy start to execute and say, ‘Wow, he’s really good at this!’”

“I was not a fan of Bell’s game,” CBS Sports’ Dane Brugler told me. “I thought he took too long to survey the field. NFL fans know him for his amazing patience, but at the college level, there was a lot of times where he would survey the field and teams would be on top of him by the time he figured out where he needed to go.”

The lesson?

“Because of that, I think I am a lot more open-minded to players who might look a little indecisive at the line of scrimmage,” said Brugler. “But it’s a fine line between indecisive and being patient. I think that’s kind of a constant battle when you evaluate running backs: to figure out where’s the happy medium.”

When it comes to the assessment of whether a player should be a first-round pick, Zierlein told me that pure physical explosiveness is something that teams are willing to reach for.

“The game is played by great athletes, and that’s why I do look for explosive ability,” he said. “Like [LSU running back] Leonard Fournette’s explosive ability, like Leonard Floyd [who went ninth overall in 2016 to the Bears].”

Explosiveness shows up on film, and it’s measureable through 40 times, broad jumps, and vertical jumps at the combine. While it’s easy to nitpick technique or downgrade a player for deficiencies in other areas of their game, you really can’t teach explosion.

Take Bruce Irvin. The former West Virginia pass rusher went 15th overall to the Seahawks in 2012. Many in the media had projected Irvin as a second- or third-round talent, and Seattle was panned for what was perceived to be a major reach.

“I remember the talk on Irvin was that he was too passive against the run. He couldn’t take on blockers,” Zierlein said. “How was he going to play against the run? And then Seattle takes him in the first round. It wasn’t only Seattle that had him that high, though. I know for a fact two other teams that were going to draft him in the first round if the Seahawks didn’t take him.”

So why did the league value Irvin more than the media did? His explosiveness.

“If you have the ability to make explosive plays — creating turnovers or sacks — especially on defense,” Zierlein said, “you get pushed up the draft board. Those quote-unquote weaknesses become fairly irrelevant.”

For players without that elite explosiveness, though, those weaknesses can become real concerns. The key is knowing which ones to worry about.

“With [Chiefs cornerback] Marcus Peters, I saw him give up some separation on routes, and I didn’t see the cleanest mirror and match footwork on man routes,” Zierlein said. “I saw some undisciplined behavior in the way that he covered. I thought he was a second-rounder.”

Of course, Peters has gone on to become one of the best defensive backs in the league. In two seasons, he’s intercepted 14 passes, knocked away another 46, and earned two All-Pro nods.

“Defensive back coaches get paid to tighten up their [players’] footwork, to tighten up their technique, to make them more disciplined. But being able to make plays in college” — Peters had 11 interceptions and 16 passes defended in three years at Washington — “that doesn’t go away.”

At the same time, not every deficiency can be coached up.

“You can’t always assume that something that’s coachable is going to get coached out,” said Zierlein. “One of my biggest misses of all time is [Rams tackle] Greg Robinson. I went back and looked at my old scouting report, and I had all the negatives, I had the issues that plagued him, but the mistake I made is assuming that he would just grow out of them.”

Robinson’s been a massive disappointment for the Rams since being selected second overall in 2014. He lost his job at left tackle 12 games into last season, and the team recently decided not to pick up his fifth-year option, meaning he’ll be a free agent after this season.

“His issues were with playing forward on his toes, having his weight always forward, being kind of a leaner, and that’s really more of a muscle-memory issue. So it’s very hard to correct, because once the bullets start flying, as they say, it’s very tough not to go back to your default mistakes.”

Rather than serving as proof of a player’s ability to produce, college statistics often complicate the scouting picture. Should it scare teams off if a guy has middling college numbers? How much of a bump do you give to a player for producing big numbers, especially if he did it in one of the top conferences, like the SEC? And how much do you push a guy down in your grading scale if his production came against inferior competition?

“Three misses for me, who I think kind of fit into the same category, would be [former USC quarterback] Matt Barkley, [Georgia pass rusher] Jarvis Jones, and [Alabama running back] Trent Richardson,” said Rob Rang of NFL Draft Scout and CBS Sports. “Obviously all three were big-time prospects, very well known, played at big-time programs. They all played in pro-style schemes that translate well to the NFL, and did so against elite competition. Because of all those factors, it was easier to just dismiss the lack of shuttle times with Richardson, or the average arm strength of a Barkley, and the lack of explosiveness for Jones.”

While it’s easy to ignore obvious red flags for top players at top schools, it’s just as easy to dismiss someone who beats up on inferior competition.

“I had [Cardinals running back] David Johnson as a fourth-round pick,” Bleacher Report’s Matt Miller said. “And I’d seen him in person a couple times. I was like: ‘He’s powerful, he’s fast, and he catches the ball well.’ He had that great kick return against Illinois State. But I think I just let the level of competition thing just sink in way too much.”

For scouts, it’s important to remember that when considering production, sometimes collegiate players will put up big numbers in a way that’ll never work in the pros.

“Bjoern Werner was really ranked high on my board, one of my top-10 prospects,” said Eric Galko of Sporting News and Optimum Scouting. “He was productive in college (23.5 sacks in three seasons at Florida State), but he was a bit shorter, a bit stockier, he didn’t really have the long athleticism, and at the NFL level, you can’t come into the league already maxed out (in physical potential). Production at the college level can almost become a bad thing; it can be misleading.”

On the other hand, there’s former LSU pass rusher Danielle Hunter, a prospect that Galko had rated in the late second to early third round. Hunter showed flashes of potential as a sack producer and tested well at the combine and his pro day, but 1.5 sacks in his final season for the Tigers didn’t really paint the picture of a guy who would rack up 12.5 sacks for the Vikings last year. Hunter clearly hadn’t put it all together.

“What I think Hunter taught me is that at some positions, [you can stomach] a lot of volatility,” said Galko. “As a pass rusher, he lacked intensity, and certainly the athletic testing was there to say he could get a lot better, but you don’t need to worry about these guys having it all figured out. You don’t need to get penetration or get into the backfield 45 to 50 times a game. If you can get, like, five pressures, a sack, and a tackle for a loss, that’s only seven snaps you did that on, and that’s a great game.”

Just about everyone missed on Cowboys quarterback Dak Prescott, who played himself into the MVP conversation as a rookie fourth-round pick last season. But while Prescott proved a lot of evaluators wrong, he also benefited from falling into a near-perfect situation.

“Having the running game that he had, the offensive protection that he had, and the fact that there was no expectations for him [all helped],” Rang said. “And the one throw that I thought that he always did very, very well was the back-shoulder fade. And, of course that’s one of the things Dez Bryant is at his absolute best at.”

So while what Prescott achieved as a rookie was incredible, who knows what the former Mississippi State star would have looked like had he not gone to a system that perfectly suited his skill set.

“I’m a firm believer that quarterbacks can be broken,” Galko said. “It’s tough to know whether [a given player is] breakable or not, but [Mark] Sanchez got broken — he played too early, he wasn’t ready. I think [Blaine] Gabbert had the same issues. [In Jacksonville], he went into maybe the worst situation for a quarterback in the modern era.”

Empty-seeming phrases like “love of the game” and “work ethic” get thrown around way too liberally on draft day, but there’s a kernel of truth in them. It takes long hours in the weight room and film room, and a certain amount of disregard for the physical punishment your body takes week in and week out during a season to make a career in the NFL, let alone to be a star.

“When Joey Harrington came out of Oregon, I’ll never forget sitting there and watching that tape and believing in him,” said Bryan Broaddus, a former scout and personnel executive with the Packers, Eagles, Jaguars, and Cowboys. “The mobility, the smarts, the accuracy, all those things. The Lions took him no. 3 overall, and I remember thinking, ‘This guy’s going to play for the long term.’ But I just don’t think Harrington really loved football.”

“I watched [cornerback] Justin Gilbert play in the Big 12 for three years,” said Miller. “He’s this 6-foot-tall, 200-pound corner that ran a 4.37, his three cone was sub-seven seconds, he was strong, and, athletically, he was everything you want.

“But Joe Thomas said it on Twitter. This is what happens when you don’t love football. It doesn’t matter how athletic you are, if you don’t love football, you’re not going to succeed.”

The amount of data that scouts and analysts have to consider before landing on a final grade is overwhelming. Perhaps the most difficult aspect of the entire undertaking is filtering out the noise and deciding what matters.

I talked to an NFL assistant coach who also has experience scouting, and he told me that it’s not uncommon for decision-makers, whether it’s the GM or head coach that’s responsible for filling out the draft card, to get swayed by the wrong people. Maybe they have a convincing or especially charismatic coach at a certain position. That coach is pounding the table for a guy he really likes, and that GM starts to think, “Maybe our scouts are wrong.” He trusts the coach, who may not have done nearly as much work on that player as the scouting department has, and that can alter the final evaluation.

Then there’s the opposite scenario. Maybe that GM falls in love with a guy who really doesn’t fit what the coaching staff wants. He tries to fit a round peg into a square hole.

The best draft decision-makers, this coach told me, are the ones who surround themselves with people they trust and are willing to listen to. When everyone’s on the same page, the system runs more smoothly. It doesn’t guarantee success, but it makes you less likely to end up with the next famous miss.