Best available NFL free agents

Bill Polian's do's and don'ts for NFL free agency:

It is a rare thing to be able to find good value in NFL free agency. The main reason for this is that teams almost always try to keep their top players on their rosters, so if a guy gets to free agency there's a good chance it's because his team has made the determination that his future value will not equal the amount of money required to keep him.

And given that this player's team knows him better than any other in the league, that can be a concern for teams considering signing the player before the evaluation process even begins.

However, that doesn't mean that there are never values to be had (either because a team has too many good players to keep all of them, or other circumstances), or that even if a team has to overpay a little bit there aren't quality players available who are capable of helping it win.

At right you will find my 14 tips for approaching free agency, which I expanded upon in an article last year. Below you will find my grades for this year's free-agent class, with analysis included for every player who earned a B-minus grade or better. I explain my grading process throughout, but in short, A players are consistent difference-makers and B players are starters who can help their teams win.

Here is my Big Board of the best available free agents for the 2015 class.

(Note: Players are listed alphabetically within each grade, and players who were franchise-tagged or transition-tagged are included to show their relative place within the marketplace.)

A-plus

Players graded in the A range are defined as those whose talent, physical gifts, durability and production allow them to win their one-on-one battles with regularity and make a difference in winning each week. By definition, there are three-down players.

Ndamukong Suh, DT, Detroit Lions

Simply put, Suh is the best defensive tackle in the NFL. If not double-teamed, he will win virtually every time.

A

Dez Bryant, WR, Dallas Cowboys (Franchise tag)

He has a rare combination of speed, power, athleticism and hands. He's one of the most talented and most productive receivers in the league.

Randall Cobb, WR, Green Bay Packers

He is the ideal slot receiver. He has great speed, separation quickness and hands, and he is very versatile, as Green Bay used him in a lot of different ways in 2014.

Stephen Gostkowski, K, New England Patriots (Franchise tag)

I don't have a ton to say about the kickers on this list, but Gostkowski is very reliable and very consistent.

Justin Houston, OLB, Kansas City Chiefs (Franchise tag)

He is an all-around top-echelon NFL pass-rusher. He possesses outstanding power, speed and pass-rush moves.

DeMarco Murray, RB, Dallas Cowboys

He has great vision, acceleration in the hole and speed, and he's also a very good finisher at the end of runs. The only concern is his durability going forward.

Demaryius Thomas, WR, Denver Broncos (Franchise tag)

He is a solid No. 1 wide receiver in the NFL. He has outstanding speed, burst, length and jumping ability, and reliable hands.

A-minus

Jerry Hughes, DE, Buffalo Bills

He is an outstanding pass-rusher with great speed, rush techniques and the flexibility to "bore" to the passer. ("Bore" is the word I use to describe the ability of a pass-rusher to dip and drive past the blocker in order to get lower than him and gain leverage in getting to the quarterback.) He is less effective setting the edge against the run.

Terrance Knighton, DT, Denver Broncos

He has outstanding size, quickness, agility, balance and strength, and he's a very tough player. He is excellent against the run, and is better as a pass-rusher than people think.

Devin McCourty, S, New England Patriots

His combination of physical characteristics and instincts makes him one of the best safeties in the league. He has good ball skills, anticipation and savvy, and he's versatile enough to play man coverage on a slot receiver. His speed and tackling ability are both outstanding for a safety.

Jared Odrick, DT, Miami Dolphins

He possesses outstanding first-step quickness, toughness, flexibility and speed to the passer. He isn't the wide-bodied run-stopper that Knighton is, but he is an outstanding "movement" D-tackle.

Jeremy Maclin, WR, Philadelphia Eagles

He is an outstanding route-runner with good separation quickness to go with excellent speed. He also has good hands.

Pernell McPhee, OLB, Baltimore Ravens

He is a part-time player who is an outstanding speed-to-power rusher with natural pass-rush slipperiness. He's a major contributor in nickel packages. The question with him is whether he can maintain his effectiveness if asked to play full time.

B-plus

Players graded in the B range are defined as those whose talent, durability and production allow them to be productive starters who contribute to winning in the NFL. By definition, these are starters.

Mike Iupati, G, San Francisco 49ers

He ranks among the best run-blockers in the league. He possesses outstanding strength, leg drive, punch and aggressiveness. He is less effective in space when pass-blocking.

George Johnson, DE, Detroit Lions

He is an outstanding natural pass-rusher who has length, speed, power and slipperiness in getting to the quarterback.

Denarius Moore, WR, Oakland Raiders

His speed and burst are outstanding. But he lacks polish as a route-runner and as a receiver overall.

Torrey Smith, WR, Baltimore Ravens

His hands are inconsistent, but he is still very effective as a deep threat because of his excellent speed and burst.

Tramon Williams, CB, Green Bay Packers

Williams is getting older, but he still possesses great instincts, playmaking ability and a nose for the ball.

B

Akeem Ayers, OLB, New England Patriots

He didn't fit in Tennessee but found a home as a designated pass-rusher in New England. He has the length and speed to do a good job in that role going forward.

Bryan Bulaga, OT, Green Bay Packers

He is a solid all-around offensive tackle who is particularly well-suited to the Packers' offensive scheme.

Charles Clay, TE, Miami Dolphins (Transition tag)

He is a very good receiving tight end with good speed, separation quickness, hands and moves after the catch. He struggles with inline blocking due to a lack of bulk. He can also play some fullback.

Michael Crabtree, WR, San Francisco 49ers

His production was down this season because of a nagging ankle injury. He is a good route-runner with an outstanding catch radius and very good hands.

Brandon Flowers, CB, San Diego Chargers

He had a solid all-around season for San Diego after being acquired in the offseason. He is a valuable starter at a critical position.

Justin Forsett, RB, Baltimore Ravens

He had a great year in former Ravens offensive coordinator Gary Kubiak's zone running scheme. (Kubiak is now the head coach of the Broncos.) He has good acceleration in the hole, vision as a runner and the ability to avoid defenders, but his size and durability going forward are a concern.

Mark Ingram, RB, New Orleans Saints

He had a solid all-around season for New Orleans. He has very good acceleration in the hole and finishes runs well. He has dealt with injuries throughout his NFL career.

John Kuhn, FB, Green Bay Packers

For teams that utilize a fullback, Kuhn is a top value. He's a solid all-around fullback who can block, run and catch. He is a smart and versatile player.

Ryan Mathews, RB, San Diego Chargers

His problem since entering the league has been his durability. When he's on the field, he shows outstanding speed, power and finishing ability as a runner.

Rolando McClain, ILB, Dallas Cowboys

He has the capability to be a three-down linebacker. He has size, speed, instincts and a strong punch. His off-field issues have been a concern previously.

Brian Orakpo, OLB, Washington Redskins

He is a solid pass-rusher and a good edge-setter against the run in a 3-4 defense. His injury history is a concern, however.

Julius Thomas, TE, Denver Broncos

He is a receiving tight end with very good speed, hands and separation skills. Nagging injuries have been a concern. Blocking is not his strong suit.

Justin Tucker, K, Baltimore Ravens

He is a solid, reliable kicker with very good range.

Shane Vereen, RB, New England Patriots

He has speed, separation quickness, the ability to avoid defenders as a runner, really good hands and is obviously smart enough to master varied alignments as part of New England's pass package. He's also a better runner from scrimmage than most give him credit for, despite his size. He would be a good addition to almost any team because of his versatility.

B-minus

Jordan Cameron, TE, Cleveland Browns

He's an outstanding receiving tight end with good speed, excellent separation quickness and moves, and he has very good hands. His past issues with concussions, however, are a concern for any team considering signing him.

Frank Gore, RB, San Francisco 49ers

His entire career Gore has been one of the most productive north-south power runners. He's a winner whose toughness and leadership by example would be ideal for a contending team. He does have a long medical history and a lot of mileage, which are concerns.

Greg Hardy, DE, Carolina Panthers

If you based this grade on his on-field ability, he's an A. If you factor in his off-field issues, you might take him off your board entirely. The fact that he faces potential league discipline is an obvious concern. On the field, he is an outstanding natural pass-rusher with speed, power, slipperiness and good technique.

Jason Pierre-Paul, DE, New York Giants (Franchise tag)

He is an outstanding pass-rusher with very good length, first-step quickness and natural "bore." He has been hampered by a back injury so far in his career, which has to be a concern going forward.

C-plus

Players graded in the C range are defined as those whose durability, talent and production allow them to contribute to winning as a role player or a backup. Players who are graded below the C line do not appear on this list and are defined as those who fill specific backup roles on a roster and are not considered long-term players.

Kenny Britt, WR, St. Louis Rams
Antonio Cromartie, CB, Arizona Cardinals
Byron Maxwell, CB, Seattle Seahawks
C.J. Mosley, DT, Detroit Lions

C

Sam Acho, OLB, Arizona Cardinals
Mike Adams, S, Indianapolis Colts
Nate Allen, S, Philadelphia Eagles
Tyson Alualu, DE, Jacksonville Jaguars
Javier Arenas, CB, Atlanta Falcons
Joe Berger, C, Minnesota Vikings
Kroy Biermann, OLB, Atlanta Falcons
Alan Branch, DE, New England Patriots
Jasper Brinkley, ILB, Minnesota Vikings
Sergio Brown, S, Indianapolis Colts
Tarell Brown, CB, Oakland Raiders
Stevie Brown, S, New York Giants
Reggie Bush, RB, Detroit Lions
Darius Butler, CB, Indianapolis Colts
Bruce Carter, OLB, Dallas Cowboys
Quinton Carter, S, Denver Broncos
Adrian Clayborn, DE, Tampa Bay Buccaneers
Daryn Colledge, G, Miami Dolphins
Willie Colon, G, New York Jets
Dan Connolly, G, New England Patriots
Chris Conte, S, Chicago Bears
Chris Cook, CB, San Francisco 49ers
Chris Culliver, CB, San Francisco 49ers
Owen Daniels, TE, Baltimore Ravens
Brian de la Puente, C, Chicago Bears
Louis Delmas, S, Miami Dolphins
Quintin Demps, S, New York Giants
Ed Dickson, TE, Carolina Panthers
Justin Durant, OLB, Dallas Cowboys
Vladimir Ducasse, G, Minnesota Vikings
King Dunlap, OT, San Diego Chargers
Dwan Edwards, DT, Carolina Panthers
Nick Fairley, DT, Detroit Lions
Bradley Fletcher, CB, Philadelphia Eagles
Andre Fluellen, DT, Detroit Lions
Orlando Franklin, G, Denver Broncos
Doug Free, OT, Dallas Cowboys
Charles Godfrey, S, Atlanta Falcons
Jonathan Goodwin, C, New Orleans Saints
Brandon Graham, OLB, Philadelphia Eagles
Shayne Graham, K, New Orleans Saints
Jermaine Gresham, TE, Cincinnati Bengals
David Harris, ILB, New York Jets
Ryan Harris, OT, Kansas City Chiefs
Geno Hayes, OLB, Jacksonville Jaguars
Mark Herzlich, ILB, New York Giants
Roy Helu Jr., RB, Washington Redskins
Darrius Heyward-Bey, WR, Pittsburgh Steelers
Davon House, CB, Green Bay Packers
Brian Hoyer, QB, Cleveland Browns
Rodney Hudson, C, Kansas City Chiefs
Karl Klug, DT, Tennessee Titans
Dawan Landry, S, New York Jets
Jeffrey Linkenbach, OT, Kansas City Chiefs
Dwight Lowery, S, Atlanta Falcons
Rey Maualuga, ILB, Cincinnati Bengals
Taylor Mays, S, Cincinnati Bengals
Brice McCain, CB, Pittsburgh Steelers
Darren McFadden, RB, Oakland Raiders
Brandon Meriweather, S, Washington Redskins
Tony Moeaki, TE, Seattle Seahawks
Rahim Moore, S, Denver Broncos
Sterling Moore, CB, Dallas Cowboys
Derrick Morgan, DE, Tennessee Titans
Mike Nugent, K, Cincinnati Bengals
B.J. Raji, DE, Green Bay Packers
Cory Redding, DE, Indianapolis Colts
Brooks Reed, LB, Houston Texans
Stevan Ridley, RB, New England Patriots
Patrick Robinson, CB, New Orleans Saints
Carlos Rogers, CB, Oakland Raiders
Antrel Rolle, S, New York Giants
Eddie Royal, WR, San Diego Chargers
Mark Sanchez, QB, Philadelphia Eagles
Dane Sanzenbacher, WR, Cincinnati Bengals
Da'Norris Searcy, S, Buffalo Bills
George Selvie, DE, Dallas Cowboys
O'Brien Schofield, OLB, Seattle Seahawks
Lawrence Sidbury, OLB, Tampa Bay Buccaneers
Jabaal Sheard, DE, Cleveland Browns
Cecil Shorts, WR, Jacksonville Jaguars
Anthony Spencer, DE, Dallas Cowboys
Brandon Spikes, ILB, Buffalo Bills
Jacob Tamme, TE, Denver Broncos
Darryl Tapp, DE, Detroit Lions
Brandon Tate, WR, Cincinnati Bengals
Daniel Thomas, RB, Miami Dolphins
Cassius Vaughn, CB, Detroit Lions
Kevin Vickerson, DT, Kansas City Chiefs
Leon Washington, RB, Tennessee Titans
Sean Weatherspoon, OLB, Atlanta Falcons
D.J. Williams, ILB, Chicago Bears
Jimmy Wilson, S, Miami Dolphins
Kyle Wilson, CB, New York Jets
Stefen Wisniewski, C, Oakland Raiders
Jason Worilds, OLB, Pittsburgh Steelers
Shareece Wright, CB, San Diego Chargers

C-minus

Terrence Cody, DT, Baltimore Ravens
Letroy Guion, DT, Green Bay Packers
Colin McCarthy, OLB, Tennessee Titans

Special veterans 

These guys aren't going to get big deals based on their age, but deserve special mention as players who were exceptionally productive during their careers. Some could potentially pay off in one-year deals with the right team.

Jay Feely, K, Chicago Bears
Jim Leonhard, S, Cleveland Browns
Terence Newman, CB, Cincinnati Bengals
Matt Prater, K, Detroit Lions
Ike Taylor, CB, Pittsburgh Steelers
Charles Tillman, CB, Chicago Bears
Osi Umenyiora, DE, Atlanta Falcons
Reggie Wayne, WR, Indianapolis Colts
Wes Welker, WR, Denver Broncos