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.

In the modern day era of free agency, the offseason has become a trampoline for suspect teams to quickly and significantly improve themselves. Very rarely these days do fans have to hear the whispered statement from general managers and owners who claim, “This will be a rebuilding year.”

Restocking an NFL team starts long before the Super Bowl is even played and reaches a peak sometime shortly after free agency begins and the draft comes to a close.

What free agents, coaches and rookies can be considered the top newcomers in the NFL this season? Who will have the biggest impact on their new teams?

Here’s a look at the top 20:

1. Terrell Owens, WR
Dallas Cowboys
For better or for worse, T.O. will have an impact on the Dallas Cowboys. Obviously, if he shuts his mouth and just plays football, the Cowboys have a legitimate claim to being the top team in the NFC East. With that said, there is no player in the entire NFL that can sink a team faster than Owens. Just ask the Eagles.

2. Al Saunders, offensive coordinator
Washington Redskins
Saunders put his mark on one of the most dangerous offenses this decade has ever seen in Kansas City and now will try to recapture the magic in D.C. The only problem is that Mark Brunell is now his quarterback instead of the super-reliable Trent Green and Saunders’ star running back is on the shelf. The offensive looked terrible in the preseason, but if Saunders can get this unit back on track, Washington might have a powerful edge in a much-heated NFC East.

3. Daunte Culpepper, QB
Miami Dolphins
If Culpepper is in fact fully recovered from a knee injury that took away most of his 2005 season, the Dolphins have finally found their man under center. Culpepper destroyed the league in ’04 and if he is even half of what he was that season, Miami is strong enough on both sides of the ball to contend with New England in the AFC East and certainly a Wild Card spot.

4. Mike Martz, offensive coordinator
Detroit Lions
“Mad” Martz takes his circus act to Motown and already has believers in QB Jon Kitna and WR Roy Williams. Anybody who watched a Lions game the past couple of years saw an offense with no direction, game plan or sense of urgency on how to fix the problem. It’s guaranteed that Martz will have all of those things and if the players buy into the system, Detroit is in a weak enough division where they could possibly make a playoff push.

5. Julian Peterson, LB
Seattle Seahawks
The Seahawks were solid, if not unexpectedly spectacular, on defense last season on their way to their first Super Bowl appearance. If Peterson can stay health, which has been a huge question mark his entire career, Seattle becomes an even better team against the run and produces one of the best linebacker corps in the NFL.

6. Herm Edwards, head coach
Kansas City Chiefs
Almost every year, the Chiefs are considered playoff contenders and almost every year, they fall short of expectations because of their defense. Insert Edwards, the defensive-minded front man who is supposed to bring a stable game plan to the weakness that is Kansas City. Will the offense suffer in Edwards’ plot to turn the defense around? Does he even have the right mix of players to accomplish the defensive overhaul?

7. Edgerrin James, RB
Arizona Cardinals
The offensive line is terrible, but the versatile James is one of the most underrated running backs in the league. He will be the new face of the Cardinals and although his numbers may take a hit this season from years past, James will still probably be worth every penny he was given by Arizona.

8. Joseph Addai, DeAngelo Williams, Laurence Maroney, RB
Indianapolis Colts, Carolina Panthers, New England Patriots
The three-headed monster shows up once again on a power rankings list, because of the potential impact they have on their respective teams. It is very possible that one, two or even all three of these rookie backs will be starting sometime this season due to injury or ineffectiveness by the starters in front of them. Ironically, each one of these top backs from the ’06 rookie class play for a potential playoff team.

9. Steve Hutchinson, OG
Minnesota Vikings
Hutchinson and Bryant McKinnie form one of the best left sides of an offensive line in the league. The Vikings laid out a lot of money to acquire Hutchinson’s services from Seattle and nobody is happier than running back Chester Taylor (another potentially solid newcomer), who gets to run behind these excellent blockers.

10. Brian Griese, QB
Chicago Bears
It wouldn’t be going out on a limb to suggest Griese should be the Bears’ starter heading into the season and not Rex Grossman. Chicago fans love Grossman, but Griese gives the team its best chance to win. With the Lions not as far behind as some people might think, the Bears are going to need their best players on the field at all times.

11. John Abraham, DE
Atlanta Falcons
When the Falcons lost defensive end Brady Smith to injury for most of last season, fellow d-end Patrick Kerney took the biggest hit. Kerney and line-mate Rod Coleman were consistently double teamed, which allowed teams to run on Atlanta with more success and hampered the Falcons pass rush. Not anymore. People forget how dominating a pass rusher Abraham can be and now that Atlanta has added DT Grady Jackson to the mix, teams are going to have a hard time double-teaming anybody on the Falcons defensive line.

12. Darren Howard, DE
Philadelphia Eagles
This is another end that can make his team more complete in the trenches. Howard was lost in the Saints’ miserable defense for many years and now that he can lurk in the shadows of fellow end Jevon Kearse, he will make a rebounding Eagles defense more sack happy than they were a year ago.

13. Javon Walker, WR
Denver Broncos
Before Walker had season-ending surgery after playing just one series last season, he showed the kind of potential in 2004 that could make him one of the game’s most dangerous receivers. There was always something missing to Ashley Lelie’s game in Denver and now the Broncos will have a well-rounded receiver in Walker to complement Rod Smith. Instead of having one stud pass-catcher and a large drop-off at the No. 2 receiver like most teams have, the Broncos now own a pair of wide outs who are fundamentally sound and who are willing to go into traffic to make the tough catch.

14. Drew Brees, QB
New Orleans Saints
The Aaron Brooks era is finally over in New Orleans and by the warm welcome fans gave Brees upon his arrival to the city, the Saints’ faithful can’t be any happier Brooks now dons sliver and black. Brees is a Pro Bowler and a proven winner, but can he do it without TE Antonio Gates and RB LaDainian Tomlinson by his side? The combination of Reggie Bush and Deuce McAllister helps ease the transition from not having LT, but Ernie Conwell can’t hold Antonio Gates’ jock.

15. Keyshawn Johnson, WR
Carolina Panthers
The plan is to have Johnson take a lot of pressure off Steve Smith by commanding attention his way so that Smith will see far fewer double (and sometimes triple) teams. That’s the plan. The reality of the situation is that both receivers’ love getting their hands on the ball and this experiment could be over sooner than it starter.

16. LaVar Arrington, LB
New York Giants
One of the more highly sought after free agents this offseason was Arrington, who decided to stay in the NFC East and play for the G-Men. Was Arrington worth all the money New York threw at him? He will be if he can stay on the field for once and start living up to the hype he created coming out of Penn State a few years ago.

17. Willie McGinest, LB
Cleveland Browns
McGinest fits extremely well into the 3-4 scheme that head coach Romeo Crennel has in place in Cleveland because, well, McGinest has played his entire career in a 3-4. But that’s not the reason McGinest is on this list. McGinest’s veteran leadership, Super Bowl-winning success and willingness to teach younger players are all going to leave a bigger impact on the team than his actual play.

18. Mario Williams, DE
Houston Texans
It’s probably safe to say that Williams won’t give the Texans all they need to win a Lombardi Trophy this season. A strong rookie showing from the No. 1 overall pick, however, would certainly go a long way in easing people’s minds in Houston.

19. Reggie Bush, RB
New Orleans Saints
Bush will find his way onto the field in some capacity and he will make teams have to scheme a little bit to stop him. He doesn’t have the same impact as fellow rookie running backs right now because of Deuce McAllister, but Bush will have a big impact on fans and the city of New Orleans.

20. Adam Vinatieri, K
Indianapolis Colts
Think Peyton Manning will ever refer to Vinatieri as an idiot kicker? Doubtful, but then again, Vinatieri probably won’t blow chip-shot field goals in huge playoff games either.