NFL Free Agents 2015: Biggest Boom-or-Bust Players Hitting Open Market

Not all NFL free-agent deals are created equal.

Any fan with a modicum of understanding about how the league works knows this. The reported terms of contracts are never the actual terms of deals. Artificial seasons with high base salaries are baked into long-term contracts for immediate salary-cap relief, bonus types and structures can be altered at any moment, and even something as supposedly straightforward as "guaranteed money" can sometimes be anything but.

The concept of boom-or-bust contracts also doesn't mean the same thing in other leagues. The Charlotte Hornets handing Lance Stephenson a $27 million contract was a risk that's gone bust. The NFL's version of Stephenson would have been handed a deal structured in such a way to make it easy for his team to get out of the deal after a single season.

Mid-tier contracts don't mean as much. In most cases, they are one-year deals given inflated numbers to make the player and his agent look better than reality.

What makes a boom-or-bust deal in the NFL is the ability to haunt you in the future. The Carolina Panthers, for instance, not only overpaid Jonathan Stewart and DeAngelo Williams for years but structured their contracts in an impossibly difficult fashion. Stewart and Williams probably would have been cut years ago under a better deal structure. As it stands, Carolina is actually paying more money to cut Williams this year than it would have to keep him, per Spotrac.

That is what you call a bust contract. With that in mind, let's take a look at a few candidates to receive such contracts.

TE Julius Thomas

How much of his production was due to a "Peyton bump"? That's the question you need to ask with any pass-catcher who's played with Peyton Manning. Eric Decker bolted Denver for New York last season and saw significant drops in production across the board. While that's partially due to the downgrade from Manning to Geno Smith, teams very rarely factor that into their contract offers.

Thomas is an interesting case because of the way his performance tapered off as 2014 progressed. He had nine touchdowns through four weeks and was seemingly on his way to blasting every tight end scoring record on the books. Then injuries and other factors—notably Manning looking in other directions—left Thomas with nondescript numbers overall.

Take away the 12 touchdowns, and Thomas' 43 receptions and 489 yards suddenly look suspect. Even his healthiest statistics in 2013 tell the story of someone who's more of a red-zone threat than a focal point to an offense. A Jimmy Graham situation this is not.

That said, the Manning Halo plus the need a ton of teams have at tight end might lead to a Graham-esque contract. Odds are Thomas' next team regrets it if negotiations go from "very good tight end" to "foundational superstar" territory.

WR Randall Cobb

There are some obvious similarities between Cobb and Thomas. Their counting stats were artificially inflated some by playing with the best quarterbacks in the world. It's unclear how they would perform without those quarterbacks because we've never seen them do it over an extended basis. (Cobb was also hurt in 2013 when Aaron Rodgers went out.)

And, most importantly, there is a very good chance they're the best players available at their respective positions. Demaryius Thomas and Dez Bryant receiving the franchise tag opened the world wide for Cobb. The only relatively comparable player on the market is Jeremy Maclin, who is probably an excellent bet to remain in Philadelphia.

Wait out the market for even a day or two, and Cobb could suddenly find himself as the only Pro Bowl-caliber wideout on the open market. While this is considered a strong draft class for receivers, few have the potential to do what Cobb's already done. His 91-reception, 1,287-yard, 12-touchdown line from last season is what you aspire your draftees to be.

Cobb's already done it, can fill a variety of roles within an offense and doesn't turn 25 until August. That's typically the type of player you'd be comfortable breaking the bank for. But teams in dire wide receiver straits aren't typically doing so hot at quarterback, either. Moving Cobb away from Rodgers takes away the No. 1 thing that makes him so great. 

DT Nick Fairley

Fairley has appeared in 46 NFL games. He's been a productive NFL player for roughly eight of them. The former first-round pick enters free agency as a bit of an enigma. Lazy and unmotivated for his first three seasons in Detroit, Fairley came into 2014 with a renewed attitude and smaller waistline.

He responded with the best extended run of football of his career, making 14 tackles and a sack in the first eight games of 2014. The numbers don't sound nearly as sexy as the results. Fairley was a wrecking ball against both the run and pass, consistently generating penetration alongside Ndamukong Suh and creating perhaps the best interior line in football. 

Pro Football Focus ranked Fairley 13th in run-stop percentage and third in pass-rushing productivity through the season's first eight games. Suh, Gerald McCoy, Geno Atkins and Aaron Donald were all looking up at him from a metrics perspective. Had he been able to stay on the field for all 16 games and kept up that level of production, there's no telling how high his market value would have gone.

Of course, he didn't. Fairley suffered a knee injury that cost him the entire second half. Now all teams have to go on in evaluating him are those eight games. It's the most recent film we have, so it's the most accurate representation of who he is, yet...yikes.

Fairley is going to get $15-20 million in guarantees on the basis of a half-season's worth of work. Keep in mind this is a dude the Lions thought so little of a year ago that they declined his fifth-year rookie option. Thirty-eight games said Fairley was a rotational defensive tackle at best. Eight said he's a star. Some team is going to pay the premium for the latter.

Good luck.

Follow Tyler Conway (@tylerconway22) on Twitter