All linebackers aren't the same. An inside linebacker is different from an outside linebacker. A linebacker who excels in a 4-3 scheme might be a bad fit in a 3-4 system.

Yet, there are some skills all linebackers need to have, like instincts, recognition, quickness, range and the ability to shed blocks. Durability is important, too. It's a collision position, you know.

Sporting News solicited the help of one NFL team's assistant director of player personnel to rank and analyze the top 20 linebackers going into the 2010 season. A look at the scout's rankings:

1. Ray Lewis, Ravens (3-4 ILB)
He has three–down ability because of his leadership, experience, instinct and bottom-line production. Despite his age, he remains an elite player.

2. DeMarcus Ware, Cowboys (3-4 OLB)
He has a good combination of size, speed, quickness and strength. His abilities to defend the run and rush the passer make him a dual problem for any offense.

3. Patrick Willis, 49ers (3-4 ILB)
Not only is he a good run defender—with instincts, athleticism and ball awareness—but he also can play in space.

4. James Harrison, Steelers (3-4 OLB)
Despite his lack of prototypical size, he is a steady producer vs. the run and pass. His natural leverage, instinctive play and use of hands help him overcome his size limitations.

5. LaMarr Woodley, Steelers (3-4 OLB)
He can play the run effectively on first and second down and can rush the passer by using strength/power or hands/finesse.

6. Jon Beason, Panthers (4-3 MLB)
He brings toughness, effort and competitiveness week in and week out. He might be better as a one-gap defender, stacking and shedding blocks, but he recognizes plays and gets to the ball quickly.

7. Jonathan Vilma, Saints (4-3 MLB)
He is instinctive with good read-and-react ability and pursuit. He is better on the move than as a pure downhill run plugger.

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8. DeMeco Ryans, Texans (4-3 MLB)
He is emerging as a good inside player because of his athletic ability, inline quickness and recognition skills. He can beat opponents with his speed but is equally willing to stack and shed a block.

9. Terrell Suggs, Ravens (3-4 OLB)
He is physical enough to play the run but also brings value as a pass rusher. He also can line up as a 4-3 end.

10. Calvin Pace, Jets (3-4 OLB)
His productivity with the Jets has been steadier against the run than the pass, but he still has the skills to rush and threaten an offensive tackle.

11. Brian Cushing, Texans (4-3 OLB)
His pending four-game suspension notwithstanding, Cushing is a fast riser who is a productive tackler, can drop in coverage and also be an effective blitzer.

12. Jerod Mayo, Patriots (3-4 ILB)
He can play the run laterally or downhill and can defeat a block or flow with the traffic when the play is away from him. He is above average in coverage, too.

13. London Fletcher, Redskins (3-4 ILB)
A career overachiever who lacks prototypical measurable skills, he compensates with excellent instincts, good inline quickness and recognition skills.

14. Karlos Dansby, Dolphins (3-4 ILB)
He has the size and athletic ability to play in the box and also get outside to make tackles along the sideline. He also is effective in coverage.

15. Lance Briggs, Bears (4-3 OLB)
He might be best on the move rather than plugging and leaning on bigger blockers. He adds value with his coverage ability on third down.

16. Lofa Tatupu, Seahawks (4-3 MLB)
He is a good run-and-hit player who understands angles and has good instincts and recognition skills. He might have been higher on this list if he hadn't missed 11 games last season because of a torn pectoral muscle.

17. Bart Scott, Jets (3-4 ILB)
The team's defensive leader, he brings toughness, accountability and confidence in his understanding of the scheme.

18. Nick Barnett, Packers (3-4 ILB)
He is steadily productive against the run and is a solid zone player on pass plays.

19. Brian Urlacher, Bears (4-3 MLB)
Although he has started to show signs of decline because of age and injuries, he still is a factor with his size, experience, strength and instincts.

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20. Elvis Dumervil, Broncos (3-4 OLB)
Like Harrison, he lacks the prototypical size as a 3-4 outside backer but is a good edge rusher. His natural leverage is an asset against the bigger offensive linemen.

Five who didn't quite make the cut

Chad Greenway, Vikings (4-3 OLB)
This under-the-radar performer is a dependable starter and a steady producer.

David Harris, Jets (3-4 ILB)
He can play capable coverage between the numbers but lacks extended range and the ability to close when plays are away from him.

Clay Matthews, Packers (3-4 OLB)
He can have an impact in every dimension of their scheme. He isn't going to push opponents back but has good lateral mobility.

Shawne Merriman, Chargers (3-4 OLB)
You still can win with him, but you can't hide his decline in productivity and playing time because of injuries.

Joey Porter, Cardinals (3-4 OLB)
He has lost some effectiveness at the point of attack in the running game and lacks the same burst off the edge he used to have. He might be only a short-term solution for Arizona.

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