Throughout the preseason, we’ll take a look at the best – and worst – the NFL has to offer, unit by unit. Look for a new set of rankings every few days. This will be the final edition!

In 1985, the Chicago Bears had one of the nastiest defenses the NFL had ever seen. The unit was so good the Bears did the Super Bowl shuffle in January and that defense is regarded as one of the best squads ever to be assembled.

In 2000, the Baltimore Ravens’ defense mirrored the ’85 Bears en route to a Super Bowl Championship of its own, even though the Ravens had less to work with on the offensive side of the ball.

Any team with a solid defense gives hope to playoff dreams – even if the franchise doesn’t have the offense to go with it. An NFL defense is often the backbone of the team without all the flash and pizzazz the offense usually generates.

Which teams are the hardest to move the ball against on the ground and what units make going over the middle for short passes virtual suicide?

Here’s a look at the NFL’s top 10 defenses:

1. Chicago Bears
The Bears defense held opposing teams to fewer than 10 points on eight separate occasions in 2006. Led by Pro Bowler and NFL Defensive Player of the Year Brian Urlacher, Chicago put any doubts created by the offense to rest and eventually wound up playing at home in the playoffs. Nathan Vasher was a pleasant surprise at cornerback and if Mike Brown can stay healthy, the secondary is on the fast track to dominating again this season. Defensive end Adewale Ogunleye is a handful for opposing tackles and LB Lance Briggs has great range and excels against the run as a complement to Urlacher. This unit will get pressure to repeat the success it had last year, but the Bears also hope the offense won’t put the defense in as many compromising situations as it did last season.

2. Carolina Panthers
With the return to health of Kris Jenkins on the defensive line, Carolina will push Chicago as the top defense this year. Jenkins frees up defensive ends Julius Peppers and Mike Rucker to rush the quarterback while newcomer Maake Kemoeatu will solidify an already stingy run defense. The linebackers have health concerns with middle linebacker Dan Morgan but if he can stay on the field, having converted safety Thomas Davis by his side will help Morgan make more plays. The secondary gets great contributions from corners Ken Lucas and Chris Gamble, but the safeties are a bit of a liability in pass coverage. SS Mike Minter, however, is great in run support and is a tremendous leader.

3. Pittsburgh Steelers
The heart and soul for the Steelers’ defense is strong safety Troy Polamalu. Nicknamed the Tasmanian Devil because he virtually spins in an instant to where the play is happening on the field, Polamalu shows on Sunday what the Pittsburgh D is really all about, and that is being relentless while trying to making plays. It all starts with Casey Hampton in the middle of the defensive line. Hampton is the immovable object in the run defense and that allows Joey Porter and Clark Haggans to make plays in the box and in the flats. Inside linebackers Larry Foote and James Farrior are steady tacklers, as are Polamalu and newly acquired Ryan Clark. Deshea Townsend and Ike Taylor are vastly underrated at cornerback and Bryant McFadden can step in at any moment and start for Townsend.

4. Denver Broncos
A lot of media pundits questioned why the Broncos went out and acquired four ex-Cleveland Browns’ defensive linemen last offseason. Well, nobody is questioning the moves now. Ebenezer Ekuban, Courtney Brown, Michael Myers and Gerard Warren comprised a unit that turned out to be superb against the run. Granted, they didn’t generate any pass rush, but that’s what linebacker Ian Gold, D.J. Williams and Al Wilson are there for. The trio in the middle of Denver’s defense all run well, tackle well and can create enough pass pressure through blitzing that the d-line can stand pat. Another great strength for the Broncos’ defense is its secondary. CB Champ Bailey doesn’t get enough credit for how well-rounded he is. Put him on an island, in the slot, up against the run, blitzing, whatever – Bailey will get the job done. First year players Darrent Williams and Domonique Foxworth played exceptionally well last year and SS John Lynch is still giving receivers a hard time when they come over the middle.

5. Jacksonville Jaguars
People forget how good Jacksonville’s defense can really be, but the Jags have a tremendous line, an above average linebacker corps and a solid secondary. John Henderson, Marcus Stroud, Paul Spicer and Reggie Hayward form a defensive line unit that is easily top five in the league. Stroud has made the Pro Bowl three seasons in a row while Hayward and Spicer combined for 16 sacks last season. The secondary is set with the offseason addition of Brian Williams, Donovin Darius is a big hitter who missed most of last season with a torn ACL injury, and FS Deon Grant has started all 32 games the past two years, so there is no doubting his durability. Rashean Mathis has Pro Bowl potential at the other corner position and Mike Peterson is the glue that holds the defense together from his middle linebacker spot. Peterson has a high motor and has led the team in tackles the last three seasons.

6. Indianapolis Colts
What has made the Colts’ defense so successful under Tony Dungy’s cover-2 scheme is the fact that the line can create pass pressure without the need for a lot of blitzing from the linebackers. It all starts with the ends – Dwight Freeney and Robert Mathis create enough havoc in opponents’ backfields that linebackers Gary Brackett and Cato June can drop into coverage. Freeney is one of the league’s most feared pass rushers and Raheem Brock will rotate in with Mathis to make sure the d-line can stack up well against the run. The secondary is loaded at safety. Mike Doss and Bob Sanders are young and can play the run exceptionally well. The cornerbacks are probably the weakness on this unit, but Nick Harper and Jason David know their roles in the cover-2 scheme, and that’s all Dungy can ask for.

7. Tampa Bay Buccaneers
The concern with this unit is that they have several players who have already had their 30th birthday, but coordinator Monte Kiffin is one of the NFL’s best defensive architects. His Tampa-2 defense will give opponents fits again this season and it doesn’t matter how old his players are. Simeon Rice struggles against the run, but his pass rushing abilities are unquestioned, and his fellow end Greg Spires doesn’t lack in the art of the sack either. Derrick Brooks is still the leader of this unit and Ronde Barber is one of the most complete cornerbacks in the game (much like Champ Bailey). The safeties are a bit of a concern, but Kiffin has enough in place to keep Tampa in every game even if the offense sputters a little while QB Chris Simms gets more experience.

8. Baltimore Ravens
If the Ravens have any hope of getting back to the playoffs after two years of struggles, the defense is going to have to step back up to its previously dominating level. Middle linebacker Ray Lewis has been injury prone and unable to stay on the field, but the Ravens’ brass has commented how motivated and determined he was in training camp. If Lewis can get back to destroying the careers of running backs, safety Ed Reed should once again look like the player that earned NFL Defensive Player of the Year honors just two seasons ago. Reed struggled in 2005 while battling through injuries himself, but a comeback is definitely in order. He’ll have help with Chris McAlister and Samari Rolle, who form possibly the best cornerback tandem in the league. Terrell Suggs, Adalius Thomas and Trevor Pryce complete the rest of the pieces to this stacked defense.

9. The NFC East Beast Defense
Okay, it’s time to have a little fun. Considering one could make an argument for each team’s defense in the NFC East, it’s time to form the NFC East Beast Defense. The unit starts with using the defensive ends from the NY Giants – Michael Strahan and Osi Umenyiora, two sack artists to get after the QB. Since the G-Men’s interior is a little thin on the line, I’ll barrow Joe Salave’a and Cornelius Griffin from the Redskins’ d-line to clog the middle. Next, the Cowboys linebackers are fast, young and versatile against both the run and pass. DeMarcus Ware, Bobby Carpenter and Akin Ayodele will man the middle. Finally, the safeties from the Eagles (Brian Dawkins and Michael Lewis) will fit nicely with the cornerbacks from the Redskins (Carlos Rogers and Shawn Springs) to complete the secondary. Was that not fair? Come on, live a little!

10. San Diego Chargers
The secondary is so bad on this group that I hesitate putting them in the top 10, but since the NFC East Beast defense was formed, the Chargers can sneak in at No. 10. The front seven is one of the best in football and linebacker Shawne Merriman might make a nice case for Defensive Player of the Year when ’06 concludes. The Chargers finished first against the run last season and a big part of that success was Luis Castillo and Jamal Williams on the defensive line. Donnie Edwards and Randall Godfrey give Merriman tons of support from the linebacker core and if free agent acquisition Marlon McCree can make the secondary just a little better, San Diego will be ranked higher here next season.

The Bottom five:

28. Kansas City Chiefs
Hey, maybe head coach Herm Edwards can improve this unit, but I’m sure Carson Palmer and the rest of Cincinnati’s explosive offensive are excited to feast on this group in Week 1. At first glance, you get excited looking at Ty Law, Patrick Surtain, Sammy Knight and Kendrell Bell on the depth chart. But then you realize that it’s 2006 and not 2003.

29. Oakland Raiders
Derrick Burgess is a stud and finished with 16 sacks to lead the league last year, but can he offer anything in run support? Warren Sapp is over the hill and although this defense is pretty fast as a whole, they’ll be victimized by teams running right down their throat (hear that LaDainian Tomlinson, Larry Johnson and [Insert Denver RB]?).

30. Houston Texans
The Texans needed way more than just Mario Williams in the draft, but hey, they’re trying to piece things together. Houston has talent – Dunta Robinson, Williams and Demarcus Faggins – but the talent is just too thin to stretch over the entire defense.

31. New Orleans Saints
Drew Brees, Reggie Bush, Joe Horn and Deuce McAllister are all excellent skill players. Now let’s hope they can score 45 points a game.

32. San Francisco 49ers
The only good thing you can say about the 49ers’ defensive unit is that Many Lawson may compete for rookie of the year honors this season because he may have to make every single tackle for San Francisco.