USA TODAY Sports' top 50 NFL free agents

Nate Davis, USA TODAY Sports | USATODAY

NFL free agency chatter is already underway, but players with expiring contracts can't officially begin switching teams until 4 p.m. ET on Tuesday (they can re-sign with their own teams at any time), by which time all 32 teams must comply with the $123 million salary cap for 2013. Who could be hitting the market? Here's USA TODAY Sports' top 50 available players:

1. Greg Jennings, WR, Packers: Yes, at 29 he's three years older than Mike Wallace and lacks his elite speed. But we love Jennings' smarts, hands and route running —not to mention his demeanor — and believe the injuries he suffered in recent years were more fluky than chronic. Imagine how effective he might be with the benefit of a ground game on a team that badly needs a wideout after trading its best one ... Best fit: Vikings

2. Mike Wallace, WR, Steelers: We'd like to see him polish his all-around game. But he's got the tools to be special and already stretches every defense, creating opportunities for himself and his teammates. Best fit: Dolphins

3. Paul Kruger, OLB, Ravens: He had nine sacks in a breakout 2012 season before adding 4½ in the playoffs. Only 27, Kruger has just seven starts in four seasons, so there's every reason to think he's far from maxing out his potential. His ability to line up at defensive end is a bonus. Best fit: Colts

4. Dashon Goldson, FS, 49ers: Coming off consecutive Pro Bowls, he could eventually stake a claim as the league's best safety. He has 14 interceptions since 2009 but will also come into the box to lay a lick on a ball carrier. Best fit: Eagles

5. Sebastian Vollmer, T, Patriots: He can play effectively on the left and right sides and is a very good pass blocker. The only red flag is a back injury that will flare up and required surgery after the 2011 season. Best fit: Patriots

6. Cliff Avril, DE, Lions: He's produced 29 sacks over the past three seasons while playing on an excellent defensive line. But can he replicate such numbers with a lesser group, and will he learn to avoid getting swallowed by run-blocking right tackles? He could very well thrive at outside linebacker for a 3-4 team. Best fit: Browns

7. Aqib Talib, CB, Patriots: More and more teams are coveting big, physical defenders like Talib (6-1, 205 pounds), who stabilized New England's secondary after arriving in a November trade. He's the best of a deep corner market. Best fit: Patriots

8. Andre Smith, T, Bengals: It all came together in 2012 for Smith, who graded out as profootballfocus.com's top right tackle. The question is whether he will maintain that level after he gets paid given the bad habits he's shown in the past. Best fit: Bengals

9. Michael Bennett, DE, Buccaneers: Martellus' brother racked up nine sacks as a full-time starter last season and was stout against the run. Best fit: Jaguars

10. Wes Welker, WR, Patriots: So many of his catches are glorified handoffs. He's caught at least 100 balls in five of his six seasons in New England and suits Tom Brady and the offense perfectly. Best fit: Patriots

11. Steven Jackson, RB, Rams: Did you know he's got more than 10,000 rushing yards, most in Rams history? But with his 30th birthday looming, Jackson realizes he probably doesn't have enough time to win a Lombardi Trophy in St. Louis, so he opted out of the final year of his contract. He could be a capstone to a contending roster. Best fit: Packers

12. Jake Long, T, Dolphins: It's rare when a perennial Pro Bowl left tackle hits the market in his prime. Long is just 27 but has ended the past two seasons on injured reserve, and there is some concern his play doesn't equate to a contract that might have to pay $10 million annually. But if the top pick of the 2008 draft recaptures his pre-injury form, he could also be a bargain. Best fit: Cardinals

13. Andy Levitre, G, Bills: Ever noticed Ryan Fitzpatrick doesn't get sacked much while Buffalo runners often gallop through gaping holes up the gut? Levitre, who deserves credit on both counts, can play anywhere on the line. Best fit: Titans

14. Keenan Lewis, CB, Steelers: Who led the AFC in pass breakups last season with 23? This guy. Like Talib, he's aggressive, big (6 feet, 208 pounds) and young (26). Best fit: Browns

15. Dannell Ellerbe, ILB, Ravens: Viewed solely through the prism of on-field production, Baltimore is better off losing Ray Lewis than Ellerbe, who made a game-saving tackle on Frank Gore at the end of Super Bowl XLVII. Best fit: Ravens

16. Connor Barwin, OLB, Texans: No way to say it nicely — he had a poor 2012 season. But past performance doesn't always portend future returns. Houston may be ready to move on to 2012 first-rounder Whitney Mercilus, but Barwin will be an asset somewhere. Best fit: Jets

17. Victor Cruz, WR, Giants: If he wasn't a restricted free agent who will come with a first-round transaction fee, he'd be much higher on this list. Chances are he's not going anywhere, though we wonder if perhaps the Rams — they own two Round 1 selections — might make a bid to sign him. Best fit: Giants

18. Tony Gonzalez, TE, Falcons: He's still the NFL's best tight end. And he'd also be ranked higher if he wasn't mulling retirement. If he buckles up his chin strap again, it will almost certainly only happen in Atlanta. Best fit: Falcons

19. Phil Loadholt, T, Vikings: This massive mauler is a major reason Adrian Peterson ran for 2,097 yards in 2012. Loadholt has missed one game in four seasons. Best fit: Vikings

20. Charles Woodson, DB, Packers: Has he lost a step? Maybe. But he's smart as a whip, leads like a general and can play deep or in the slot. He could also be the missing piece for a contender. Best fit: 49ers

21. Desmond Bryant, DT, Raiders: Young run stuffer is only 27. A Harvard education doesn't hurt, either, when it comes time to learn a new playbook. Best fit: Titans

22. Jermon Bushrod, T, Saints: Solid — if not elite — left tackle, but he's done a fine job looking after Drew Brees. Best fit: Saints

23. Ed Reed, FS, Ravens: He may not be the ball hawk he once was, but he remains a de facto coach on the field. Don't be surprised if the Patriots and/or Colts make a serious run at Reed. Best fit: Ravens

24. Chris Houston, CB, Lions: Just a complete all-around player who doesn't get enough recognition. Best fit: Lions

25. Philip Wheeler, OLB, Raiders: Took a one-year, prove-it contract last year with Oakland and more than distinguished himself. Best fit: Cowboys

26. John Abraham, DE, Falcons: Too old? Sure, he's about to turn 35, but he's averaged 11 sacks over the past three seasons. He should fit in 3-4 or 4-3 schemes. Best fit: Seahawks

27. Reggie Bush, RB, Dolphins: He's known for ankle-breaking runs and game-changing ability. He deserves more credit for his leadership and improved durability. Best fit: Lions

28. Jared Cook, TE, Titans: Tennessee has done a poor job fully implementing Cook's talents into their gameplans. But team brass sure sounded committed to harnessing his ability at the combine even though Cook was ultimately not franchised. Too bad he might get away. Best fit: Browns

29. Phil Dawson, K, Browns: Who cares if he's 38? Over the past four seasons, he's drilled 87% of his field-goal attempts, many in poor conditions: Best fit: Seahawks

30. Louis Vasquez, G, Chargers: Given the relatively poor blocking in front of Philip Rivers in recent seasons, it's difficult to fathom why San Diego hasn't re-signed underrated Vasquez yet. Best fit: Colts

31. Israel Idonije, DE, Bears: He's been overshadowed in Chicago, but he's a complete player who also excels as a kick-blocking special teamer. Best fit: Buccaneers

32. Osi Umenyiora, DE, Giants: He's vowing to emerge as the defensive player of the year this season. Sacks won't be a problem, but you're gonna have to stop the run better, Osi. Best fit: Falcons

33. Sean Smith, CB, Dolphins: At 6-3, 218 pounds, he's enormous. Seems like the ideal guy to line up opposite Calvin Johnson, Brandon Marshall and Jordy Nelson. Best fit: Vikings

34. Eric Winston, T, Chiefs: Penalties are a bit of an issue. But you can essentially plug him into the right side of your line and then worry about something else. Best fit: Rams

35. Brandon Moore, G, Jets: He's been overshadowed by Pro Bowl teammates in New York, but this guy's a beast, especially when he's moving forward. Best fit: Bears

36. Dwight Freeney, DE, Colts: He did OK at outside linebacker last year in Indy, but his best position is right end on a four-man front. Best fit: Patriots

37. Ahmad Bradshaw, RB, Giants: He's productive. He's tough. He's great in pass protection. He's also had chronic foot problems that will drive down his price and should limit his touches. Best fit: Falcons

38. Danny Amendola, WR, Rams: The NFC's version of Welker is also an outstanding return man. Best fit: Eagles

39. Dominique Rodgers-Cromartie, CB, Eagles: Could revert to Pro Bowl form with a fresh start. Best fit: Buccaneers

40. James Harrison, OLB, Steelers: Bum knee cost him burst off the edge in 2012 (six sacks were a career-worst as starter), but he still thrived at knocking down running backs. Best fit: Browns

41. Mike DeVito, DE, Jets: You've probably never heard of him, but gap-plugging ends on 3-4 defenses tend to go unnoticed. Best fit: Bills

42. Glover Quin, S , Texans: Houston values the versatility of a guy who used to start at corner. Best fit: Texans

43. Gosder Cherilus, T, Lions: Detroit can move on to last year's top pick, Riley Reiff. But Cherilus' protection will be a boon to another young passer. Best fit: Colts

44. Martellus Bennett, TE, Giants: Good combination tight end just turned in career year with New York. Quirkly personality can take some getting used to. Best fit: Titans

45. Brandon Gibson, WR, Rams: Owns amazing hands and has surpassed 50 grabs in two of past three seasons. Ideal guy to ride shotgun to a No. 1 wideout. Best fit: Bills

46. Dustin Keller, TE, Jets: He picked a bad year to be dogged by a bum ankle. Someone will get a steal considering Keller averaged 60 catches, 751 yards and five TDs in the previous two seasons. Best fit: Dolphins

47. Brent Grimes, CB, Falcons: Got slapped with the franchise tag last year, then blew out his Achilles on opening day. He'll have to re-establish his value, and the best way to do that might be staying put. Best fit: Falcons

48. Donald Thomas, G, Patriots: He's going to make some tailback very happy. Best fit: Chargers

49. Sam Baker, LT, Falcons: He flashed the ability last season, but can he stay off the operating table? Best fit: Dolphins

50. Shonn Greene, RB, Jets: He's a decidedly ordinary, two-down back. He also shows up every week and would be quite a capable clock killer for a contender. Best fit: Steelers

BEST OF THE REST (listed alphabetically)

Quarterbacks: Derek Anderson, Jason Campbell, David Carr, Chase Daniel, Bruce Gradkowski, Rex Grossman, Josh Johnson, Byron Leftwich, Matt Leinart, Josh McCown, Luke McCown, Brady Quinn, Drew Stanton, Tyler Thigpen.

Running backs: Cedric Benson, Ronnie Brown, Justin Forsett, Peyton Hillis, Rashad Jennings, Felix Jones, Rashard Mendenhall, Kevin Smith, Michael Turner, Beanie Wells, Danny Woodhead.

Fullbacks: James Casey, Jerome Felton, Greg Jones.

Wide receivers: Donnie Avery, Austin Collie, Julian Edelman, Devery Henderson, Michael Jenkins, Mohamed Massaquoi, Randy Moss, Louis Murphy, Jerome Simpson, Brandon Stokley.

Tight ends: Dallas Clark, Fred Davis, Anthony Fasano, Brandon Myers, David Thomas, Delanie Walker, Ben Watson.

Tackles: Khalif Barnes, Nate Garner, Winston Justice, Sean Locklear, Bryant McKinnie, Tyler Polumbus, Barry Richardson, Geoff Schwartz, Max Starks, Will Svitek, Jeremy Trueblood.

Guards: Kevin Boothe, Ramon Foster, Tyronne Green, Leroy Harris, Doug Legursky, Lance Louis, Stephen Peterman, Mike Pollak, Matt Slauson, Rob Turner.

Centers: Dan Koppen, Todd McClure, Brad Meester.

Defensive ends: Victor Butler, Andre Carter, Robert Geathers, William Hayes, Jason Hunter, Lawrence Jackson, Ropati Pitoitua, Juqua Parker, Frostee Rucker, Trevor Scott, Matt Shaugnessy, Kyle Vanden Bosch.

Defensive tackles: Alan Branch, Chris Canty, Shaun Cody, Glenn Dorsey, Dwan Edwards, Ron Edwards, Sedrick Ellis, Aubrayo Franklin, Casey Hampton, Sammie Lee Hill, Ricky Jean-Francois, Jason Jones, Ma'ake Kemoeatu, Terrance Knighton, Sen'Derrick Marks, Roy Miller, Sione Pouha, Richard Seymour, Isaac Sopoaga, Kevin Vickerson, Corey Williams.

Outside linebackers: James Anderson, Michael Boley, Justin Durant, Quentin Groves, Erin Henderson, Manny Lawson, DeAndre Levy, Calvin Pace, Shaun Phillips, Nick Roach, Daryl Smith, Erik Walden, D.J. Williams.

Inside linebackers: Nick Barnett, Chase Blackburn, Jasper Brinkley, Dan Connor, Larry Foote, Bradie James, Brad Jones, Rey Maualuga, Bart Scott, Takeo Spikes, Brian Urlacher.

Cornerbacks: Kyle Arrington, Sheldon Brown, E.J. Biggers, Darius Butler, Antoine Cason, Nate Clements, Derek Cox , Cedric Griffin, DeAngelo Hall, Kelvin Hayden, Quentin Jammer, Mike Jenkins, Adam "Pacman" Jones, Brice McCain, Captain Munnerlyn, Terence Newman, Tracy Porter, Jerraud Powers, Aaron Ross, Cary Williams.

Safeties: Ronde Barber, Yeremiah Bell, Patrick Chung, Chris Clemons, Chris Crocker, Louis Delmas, Dawan Landry, LaRon Landry, Quintin Mikell, Kenny Phillips, Glover Quin, Jamarca Sanford, Gerald Sensabaugh, Madieu Williams, Adrian Wilson.

Kickers: David Akers, Nick Folk, Shayne Graham, Jason Hanson, Steven Hauschka, Ryan Longwell, Olindo Mare, Lawrence Tynes.

Punters: Nick Harris, Donnie Jones, Shane Lechler, Brian Moorman, Sav Rocca.

Kick returners: Joshua Cribbs, Ted Ginn, Domenik Hixon, Stefan Logan, Roscoe Parrish, Darius Reynaud, Micheal Spurlock, La'Rod Stephens-Howling, Brandon Tate.

Special teamers: Lorenzo Alexander, Kassim Osgood.

NOTE: Chiefs LT Branden Albert, Bills Pro Bowl FS Jairus Byrd, Broncos all-pro LT Ryan Clady, Bengals DE Michael Johnson, Colts P Pat McAfee, Chicago Bears Pro Bowl DT Henry Melton, Dallas Cowboys Pro Bowl pass rusher Anthony Spencer and Miami Dolphins Pro Bowl DT Randy Starks all bear the franchise tag and are unlikely to switch teams.

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