NFL Free Agents 2015: Biggest Question Marks Surrounding Top Unsigned Players

NFL free agents generally funnel back to teams in waves. The very best players come off the market in an early flurry, while the top remaining assets after the craziness of the first 24 hours typically sign within the first week. 

Free agency is currently entering its next round.

Big names are still left on the market, but they all come with a caveat. Each possesses at least one undeniable question mark that is making teams hesitant about a deal and driving down the player's likely signing price. 

Savvy teams can find incredible bargains during this point in free agency. But it takes diligent sorting through messy situations to find out which of the remaining free agents have question marks that can be remedied moving forward. 

There's both diamonds in the rough and predictable busts. 

In the following slides, we'll highlight some of the biggest names left on the market and the one question mark clouding their extended stay in free agency. 

RB Stevan Ridley

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How easy it was to forget about Ridley amid New England's run to another Super Bowl.

Just two years prior to 2014, Ridley had rushed for over 1,200 yards with 12 touchdowns. Fumbling issues dogged his 2013 season, but he was still on pace for over 900 yards and six touchdowns before a knee injury stole away his final 10 games of last year.

Ridley is still only 26 years old, with limited wear on his tires as a professional (672 career touches). When healthy, he's a vastly productive between-the-tackles runner with shifty feet and power behind his pads. 

Question mark: Coming off major injury

Ridley tore his ACL in Week 6 and didn't have surgery on the knee until November. It can't be certain that he'll be anything close to 100 percent for training camp. 

WR Michael Crabtree

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Crabtree was once a rising star at his position. Emphasis on "once." A former first-round pick of the San Francisco 49ers, Crabtree finally peaked in 2012 with a breakout season consisting of 85 receptions, 1,105 yards and nine touchdowns. Then major injury struck in the form of a torn Achilles tendon suffered during the ensuing offseason. 

In the two seasons since, Crabtree has just 87 catches for 979 yards and five touchdowns over 21 games. His fully healthy 16-game run in 2014 finished with fewer than 700 receiving yards and just four scores. 

When at his best and healthy, Crabtree is an electric after-the-catch athlete capable of gaining separation at any level. He also doesn't turn 27 until September. 

Question mark: Post-injury performance

The drop off in production following his Achilles tendon tear was eye-opening. The 49ers have legitimate concerns about how the injury has changed Crabtree's game. He's just another guy without his stop-start explosion and ability after the catch. 

TE Jermaine Gresham

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Gresham never fully lived up to his first-round draft status with the Cincinnati Bengals, but there's something to be said about availability and consistent production. 

Over five years in Cincinnati, Gresham missed all of six games. He also finished every season with at least 45 receptions and four or more touchdowns. In 2014, Gresham caught 62 passes with five scores. 

He is still only 26. While Gresham is nothing more than an average middle-of-the-field receiver and capable blocker, tight ends are at a premium in the NFL. He's still one of the best 32 in the game, which probably says more about the state of the position than Gresham.  

Question mark: Surgery recovery

The free-agent period wasn't kind to Gresham. Initially linked with the Oakland Raiders, Gresham had a herniated disc discovered in his back during the courting process. According to Ian Rapoport of NFL Network, surgery was needed to fix the issue. Gresham may now need to wait until training camp—when he'll be closer to 100 percent—to find a team. 

LB Brandon Spikes

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Had Spikes played 20 years ago, he wouldn't be found on a list like this one. 

One of the game's true throwback linebackers, Spikes is a certifiable monster against the run. According to Pro Football Focus, no inside linebacker has a higher grade against the run since 2010 than Spikes—who played last season in Buffalo and his first four in New England. 

He is still only 27 years old and has no major injury issues. So what gives? The times, they are a changin'...

Question mark: Two-down player?

The modern NFL is phasing out both the running back position and linebackers like Spikes. It's hard to hold onto a job as a true run-stuffer when the NFL continues to become more and more wide open in the passing game. Spikes has obvious value as a two-down terror against the run but an evolving game continues to limit his market. 

C Stefen Wisniewski

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Centers have been paid like mad this offseason, but Wisniewski remains on the market as the best player at his position. It should be time to cash in. 

According to Pro Football Focus, Wisniewski rose to the No. 11 overall center during the 2013 season, but he dropped off and finished last year as the site's 22nd best player at the position. He is excellent in the run game, as evidenced by his plus-13.5 run-blocking grade over the last two seasons. 

Only 25, he will eventually get paid a decent deal. But why hasn't a team pulled the trigger yet?

Question mark: Pass-blocking woes

While a legitimate mover in the run game, Wisniewski's deficiencies as a center come in the passing game. He earned a negative grade in pass protection last season after only an average year in 2013. Overall, he allowed 16 pressures and one sack over roughly 650 pass-blocking snaps in 2014. Teams don't want to sign a big check to a player that could be a liability in interior pass protection. 

LB Rolando McClain

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McClain has an NFL story few can match. A former first-round pick, he has willingly retired twice—only to return to football last season and enjoy a revival season with the Dallas Cowboys. 

There's no forgetting his eventful stay in Oakland, but McClain was clearly one of the 10 best at his position last season in Dallas. He stopped the run at a ridiculous pace, covered down the field and even rushed the quarterback. He did it all for a defense many expected to be poor, especially without fellow linebacker Sean Lee. 

McClain should have a buzzing market, but it's been almost silent. And it's easy to understand why.

Question mark: Off-the-field

One good season doesn't erase a career of mistakes. A handful of arrests and a looming four-game fine for violating the league's substance abuse policy are worrisome transgressions for any club. If his head is on straight, he can be a serious asset at linebacker. But that's a big if when it comes to McClain. 

OT Jake Long

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Once one of the premier left tackles in all of football, Long has been sent to the chopping block after two mostly miserable seasons in St. Louis.

Back-to-back trips to injured reserve all but sealed his fate, as the Rams cut him as a salary-cap move this past month. He's now a 29-year-old tackle looking to rehab both his knee and his value on the open market, two difficult tasks even in a league where left tackle is still king. 

When healthy, few tackles in the game hold down the blind side better. But those dominant days seem like forever ago now. 

Question mark: Long-term health

Long is coming off ACL tears in each of the last two seasons. While not as significant an injury as in the past, stacked tears are certainly concerning. He's now a severe injury risk, and he might need a position change due to the reduced athleticism that comes with major low-leg issues. 

WR Wes Welker

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Welker is on the wrong side of 30, but he's still only two years removed from a 118-catch season in New England and just one from catching 10 touchdowns with Peyton Manning in Denver. 

Then again, Father Time is undefeated. And Welker might be his next victim. 

In his younger days, Welker was the most productive slot receiver of his era. He produced five seasons with over 100 catches while with the Patriots and eventually transitioned seamlessly to Denver's high-octane offense. But he is still struggling mightily to find a market. 

Question mark: Age, role and injury

Welker is fraught with red flags. He's now 33 years old and dealing with a lengthy concussion history, and his abilities are specific only to the slot. Will he have any market? It's possible the NFL could end his career for him. There's understandably little interest in an old, slow slot receiver.