Sometimes it's hard to figure out how NFL teams scout and sign free agents. Players with short, questionable track records land monster contracts, and players with Hall of Fame résumés coming off solid seasons can't get a sniff.
Age, injury and lack of production can all rightfully scare NFL teams away from offering big contracts to free agents—but in the middle of May, the big money has already been spent.
With OTAs just getting underway, there are still plenty of quality veterans still waiting for their phones to ring, still waiting for an opportunity to prove they can step in and make a team better.
Maybe they'll get picked up once the first wave of OTAs is complete and head coaches realize they can't scrape by with an unproven player at that position after all. Maybe their phones will ring when an injury strikes and a team needs immediate help.
Whenever each of these veterans finally finds a team that wants him, he'll be able to contribute, start or even star.
Here are the top available free agents, ranked by their immediate-impact ability.
Quentin Jammer is not a future Hall of Famer. He's never even been to the Pro Bowl. Even so, the 6'0", 204-pound cornerback has given the San Diego Chargers more than fair return for the 2002 No. 5 overall draft pick.
Jammer has been a stalwart in the Chargers secondary. An 11-year veteran, Jammer has missed only three starts since becoming a full-time starter in 2003.
That said, the 33-year-old Jammer is coming to the end of his time as a viable starter. He was Pro Football Focus' 107th-ranked cornerback out of 113 qualifiers (subscription required), marked heavily down both for his performance in coverage (minus-6.8) and for drawing nine penalties.
Nevertheless, Jammer is still a strong and willing tackler, and his experience could be valuable for a team with a young secondary. Tod Leonard of U-T San Diego was told by Jammer he'd "love to come back" to the Chargers, but even Jammer doesn't expect to be re-signed.
There's no question that Ahmad Bradshaw is more talented and was more productive last year than many backs currently on an NFL roster are or will be.
Last season, Bradshaw ran for 1,015 yards and six touchdowns on just 221 carries, picking up yardage at an excellent 4.59 yards-per-carry clip.
That said, Bradshaw's a running back coming off back-to-back foot surgeries. At 27, he should have several productive years left, but that presumes he's the same back he was before he got hurt.
Despite the Pro Football Talk report from Josh Alper that Bradshaw has been medically cleared, it's no surprise that teams are still treating him with kid gloves.
Before a groin injury sidelined him for nearly all of the 2012 season, Daryl Smith had been a solid, steady starter for his entire Jaguars career.
The 31-year-old Smith was an early second-round selection of the Jaguars in the 2004 draft, and he's more than lived up to his lofty draft position. Smith's 538 solo tackles and 141 assists make him the Jaguars' all-time leading tackler, per Pro Football Reference.
If his injury is healed, Smith should have no problem patching a threadbare 4-3 linebacking corps.
That said, if a productive-but-not-dominant linebacker (Smith has zero Pro Bowl appearances) on the wrong side of 30 coming off a severe groin injury does not have a hot market for his services, it's understandable.
Technically speaking, Nick Barnett is not physically fit to play football. At least, that's what the Buffalo Bills medical staff decided when releasing him in February.
Though Barnett struggled with a wrist issue—and subsequent wrist surgery—in 2010 and was limited in practices throughout the 2012 season because of a knee injury, there's no widely known reason why Barnett wasn't cleared. He started all 16 games of each of the past two seasons.
Assuming another team's medical staff would find nothing wrong with Barnett, he'd be a very good addition to a team needing a veteran linebacker. Turning 32 on May 27, Barnett is younger than many of the free agents on this list.
To top it all off, Barnett was Pro Football Focus' ninth-ranked 4-3 outside linebacker in 2012 (subscription required).
If Barnett truly is healthy, he should be the first outside linebacker any team that suffers a training camp injury calls.
In 2012, Quintin Mikell had arguably his best statistical season. He racked up 75 solo tackles, per Pro Football Reference, and added 18 assists. Mikell, always a standout against the run, also had a personal-best three sacks.
Pro Football Focus graded Mikell as its fifth-best overall safety (out of 88 qualifiers) in 2012; his plus-8.5 run-stuffing grade was third-best in the NFL (subscription required). Furthermore, Mikell's pass-rush grade led all safeties with a plus-8.0.
Though Mikell has never been strong in coverage, and his minus-1.9 grade slotted him 67th out of 88, he's still a perfectly capable strong safety who can come up into the box and make plays.
Jim Thomas of the St. Louis Post-Dispatch reported on May 11 that Mikell's locker is still intact. It's still possible the Rams could end up re-signing him.
Kerry Rhodes has long been an excellent two-way safety, and 2012 might have been his best season yet.
A former fourth-round pick of the New York Jets, the 6'3", 209-pound Rhodes turned in a fantastic effort backstopping the Arizona Cardinals defense. With four interceptions, six passes defensed and 63 solo tackles (nine assists), it's no wonder Rhodes ended up as Pro Football Focus's fourth-ranked safety in 2012 (subscription required).
Released due to an impending $6 million cap hit (per Spotrac.com), the market for Rhodes should have been robust.
Instead, Rhodes has visited the Bengals, per a tweet by ESPN.com's Adam Schefter, and been name-dropped by new Browns free agent Michael Lombardi (new defensive coordinator Ray Horton worked with Rhodes in Arizona), according to Nate Ulrich of the Akron Beacon-Journal.
If Rhodes's contract demands aren't demanding, he should definitely find a spot to play this summer. If not, teams are missing out on a quality free safety.
Eric Winston, 6'6", 305 pounds, has the big, athletic frame today's NFL head coaches love to see in an offensive tackle. The 2006 third-round pick has proven both his ability and his durability, having started all 16 games of each of the last six seasons.
Winston was drafted by the Houston Texans, and he worked his way into the starting lineup as a rookie. After six productive years there, he moved on to Kansas City, where he was Pro Football Focus' 26th-best offensive tackle (out of 80) and ninth-best right tackle (subscription required).
Having retained left tackle Branden Albert, though, and drafting tackle Eric Fisher No. 1 overall, the Chiefs no longer had a need for Winston's services.
Winston entered a free-agent market full of talented tackles. According to Mike Jones of The Washington Post, Winston does have a fan in Kyle Shanahan, the Washington Redskins coach who worked with Winston in Houston.
But Winston's asking price is keeping suitors away.
John Abraham was a cap casualty this offseason, getting handed his walking papers for being too old (35) and too well-paid.
He wasn't released for lack of production, though; Abraham's 10 sacks, eight quarterback hits and 38 pressures made him one of the most productive defensive ends in the NFL last season.
In fact, while switching between the right and left side to maximize his matchup, Abraham accounted for 34.5 percent of the Falcons' 29 sacks, the fifth-lowest team total in the NFL last season, per Pro Football Reference.
Yet Abraham was let go and replaced with free-agent signee Osi Umenyiora.
Still on the market months later, the Falcons reached out to Abraham about coming back on a reduced salary, according to Mike Garafolo of USA Today. Abraham, Garafolo writes, was not interested in returning to a team that released him.
Brandon Moore will turn 33 in June. Any team that signs him isn't going to be getting a powerhouse guard who can anchor the line for years to come.
However, Moore has been a fixture on the Jets line since 2005, not having missed a single start in the past eight seasons. He's gotten better as he's aged too. Moore made his first Pro Bowl after the 2011 season, and he was Pro Football Focus' fourth-ranked guard in 2012 (subscription required).
Though Moore is a better run-blocker than pass-protector, and the NFL is becoming a pass-first league, Bleacher Report's own Matt Miller graded Moore out as the No. 7 overall guard in the B/R 1000 series.
Moore has been playing at such a high level that he'd be a drop-in upgrade for nearly every team in the NFL. He may not be young enough to earn a megabuck deal like new Tennessee Titans guard Andy Levitre, but he's good enough to start for someone in 2013.