Breaking Down the Most Improved Units After 2015 NFL Free Agency

The NFL's league year opened a little over a month ago, and in the weeks that followed, the landscape of the league dramatically altered.

Positions that were once weaknesses have now become ones of strength. Units that looked feeble in 2014 now look menacing heading into 2015. One positive offseason is all that's needed to cure what ails a feeble offense or pathetic defense, and we've seen that on multiple occasions already over the past month.

On this list, we have units that were awful last year, and others that were decent to good. The common denominator, though, is that all are much better now than they were when the 2014 season wrapped.

It's time to break down the most improved units after 2015 NFL free agency.

Jets Secondary

Seth Wenig/Associated Press

Last year, the New York Jets secondary was a complete and total train wreck, allowing 31 touchdown receptions—the third-most in the NFL.

To say that won't be the case this season would be an understatement, as the Jets drastically rebuilt the unit in free agency, turning what was once a position of weakness into one of overwhelming strength.

The crown jewel of the haul is undoubtedly cornerback Darrelle Revis, who is arguably the best cover man in the NFL. Revis started his career with the Jets before spending a season each in Tampa Bay and New England, and he helped the rival Patriots win the Super Bowl this past February. Now, Revis is back on Broadway after signing a big-money deal, and while he's 29, he should be able to contribute over the life of the contract (five years).

Revis' former batterymate, cornerback Antonio Cromartie, is also once again a Jet. Cromartie spent last season in Arizona and intercepted three passes, and he will reunite with Revis to form one of the better cornerback combinations in the league. Former Browns nickelback Buster Skrine was also signed, and he brings excellent depth and ability to the position.

And the Jets added a safety too, inking former Charger Marcus Gilchrist to a four-year deal. Head coach Todd Bowles recently waxed poetic about Gilchrist to Dom Cosentino of NJ.com: "(Gilchrist has) got very good cover skills. He gives us a lot of versatility from a coverage standpoint. He has that ability to go out and cover and not be mismatched as often as we would be mismatched in a normal capacity."

Give Bowles and new general manager Mike Maccagnan credit for aggressively upgrading what was an albatross around the roster's collective neck.

Bills Offense

Gary Wiepert/Associated Press

It's crazy to think, but the Buffalo Bills might have their most talented offense in place since the famed K-Gun days of the early-to-mid 1990s.

And that's thanks to an aggressive approach to improve the offense spearheaded by new head coach Rex Ryan.

The first major move was the blockbuster trade for Eagles running back LeSean McCoy, who was immediately installed as the team's starter. Over the last two seasons, McCoy rushed for 2,926 yards and 14 touchdowns, and he'll be the centerpiece of Ryan's ground-and-pound offensive philosophy.

Tight end Charles Clay was signed away from the rival Dolphins, and while the team overpaid for him (five years, $38 million), he's clearly on the upswing. He finished last year ranked as Pro Football Focus' 14th-best tight end but is definitely on the cusp of breaking out. It should surprise no one if Clay authors an impressive 2015 season.

Wide receiver Percy Harvin was signed on a one-year contract that is sound for both player and team. The mercurial Harvin needs a positive campaign to rehabilitate his image, and Buffalo could be the perfect place. Harvin still possesses electrifying speed and game-breaking talent, and players of his ilk don't grow on trees.

And while the Bills still need a true franchise quarterback, the trade for Vikings passer Matt Cassel was a smart one. Cassel is better than incumbent EJ Manuel, and he did lead the Chiefs to the playoffs in 2010.

Don't be surprised if the Bills offense is explosive in 2015.

Eagles Running Backs

Tony Gutierrez/Associated Press

Before your face turns red and you blow a gasket: Yes, we are aware that the Philadelphia Eagles traded LeSean McCoy to Buffalo, and yes, we know that McCoy went No. 1 overall last year in your fantasy football draft.

So how is it possible that the Eagles running backs could be one of the league's most improved units after losing McCoy? Because the team added two players with the money saved who can theoretically provide more production than the artist known as Shady.

The first major signing in the Philadelphia backfield was Cowboys back DeMarco Murray—the reigning Offensive Player of the Year. Murray was majestic in 2014, combining graceful agility with brute physicality en route to 1,845 yards on the ground and 13 rushing touchdowns. Make no mistake about it: Murray is a fantastic fit for Eagles coach Chip Kelly's spread-power attack and should dominate in that scheme.

Murray's critics will point to 2014 being the only season in which he's stayed healthy and his massive workload (392 carries), which is what made the second signing so important. Kelly also inked Chargers back Ryan Mathews, and he is an excellent rusher in his own right (albeit not on Murray's level).

Mathews has averaged 4.4 yards per carry throughout his five-year career and has flashed the form of a top NFL running back, but he has also shown an inability to stay healthy. But it stands to reason that if both Murray and Mathews can spell each other—along with incumbent backs Chris Polk and Darren Sproles—the Eagles will have the most dynamic and effective backfield in the NFL.

Titans Defense

James Kenney/Associated Press

While the Tennessee Titans still (unfortunately) hold the moniker of the NFL's most nondescript team, coach Ken Whisenhunt and general manager Ruston Webster took strides toward greatly improving the defense in free agency, adding an identity to the team.

Re-signing pass-rusher Derrick Morgan was of the utmost importance, as he led the team in sacks last year with 6.5. He was the team's first-round pick in the 2010 draft and has garnered 19 sacks over the past three years, so he can definitely help coming off the edge.

The signing of Redskins pass-rusher Brian Orakpo could pay significant dividends. While he struggled through an injury-riddled 2014 season (he only contributed half a sack in seven games played), he accrued 10 sacks in 2013 and was Washington's franchise player headed into the 2014 campaign. Orakpo was the 13th overall pick of the 2009 draft, so the talent is clearly there.

An underrated transaction was the signing of Bills safety Da'Norris Searcy, who is ready to break out. He finished 2014 ranked as Pro Football Focus' 18th-best safety.

Whisenhunt and Webster also brought in 49ers cornerback Perrish Cox, who intercepted five passes last year and will add depth and talent at the position.

Seahawks Tight End

Bill Haber/Associated Press

On the iconic children's television show Sesame Street, there is a game called "Which of these things is not like the other?"—so let's apply that to the current tight ends on the Seattle Seahawks roster, shall we?

Luke Willson. Anthony McCoy. Cooper Helfet. Jimmy Graham.

If you answered Graham, congratulations—you win! Graham is not like the other tight ends listed, and that's because he is one of the best players in the league—regardless of position.

When the Seahawks dealt center Max Unger and a first-round pick in this month's draft for Graham (and a fourth-round pick), coach Pete Carroll and general manager John Schneider declared to the rest of the league that the team will be gunning for a third consecutive Super Bowl appearance. It's the kind of move that pushes a team over the top and helps it raise a Lombardi Trophy.

Graham—a three-time Pro Bowler and one-time first-team All-Pro tight end—is a phenomenal weapon in a team's passing attack, especially in the red zone, where he dominates. Graham has 51 touchdown receptions in five NFL seasons and hasn't caught fewer than 85 passes in a campaign since 2011.

Simply put, Graham could be the difference between winning and losing the Super Bowl next season for Seattle.