When separating the best from the rest, especially in boxing, every detail of a fighter’s career matters. More important than the number of wins he chalked up or the number of titles he captured are questions like who he fought and how he performed against his best opponents. Did he ever look vulnerable and how did he respond to adversity?

And when looking at the best of a decade, longevity comes into the discussion. Was the fighter able to maintain a championship pace for nearly all 10 years or just five? Battling the inevitability of getting older, did he somehow manage to improve as a fighter? Did he extend his career beyond the average expiration date or did he never recover from a particular defeat?

Whittling down the details takes time, but this system seemed a fair and accurate way to go about determining just who were the best fighters from this decade:

Setting the time parameters from 2000 to 2009 and looking at each man’s biggest fights, who was the best in the sport the longest?

With that out of the way, it’s time to unveil…

1.  Manny Pacquiao

From his breakout performance against Lehlohonolo Ledwaba in 2001 to his career-best knockout win over Miguel Cotto last month, Manny Pacquiao improved every time he stepped in the ring. During the decade, he captured titles in seven divisions, four of them linear divisional titles. He defeated three of the names on this list and next has a shot at a fourth when he takes on Floyd Mayweather Jr. in a fight that is estimated to set earnings records.

Highlights of 2011: Pacquiao vs. Mosley Fight

2. Floyd Mayweather Jr.

Undefeated in 13 years as a professional, Floyd Mayweather Jr. has proven himself the most complete fighter in the world over the last quarter century. A five-division champion with wins over Juan Manuel Marquez, Ricky Hatton, Zab Judah, Jose Luis Castillo and Diego Corrales, Mayweather now aims to cement himself as one of the greatest fighters of all time with a win over Manny Pacquiao this spring.

3. Bernard Hopkins

If  longevity is the mark of a champion, then Bernard Hopkins is Undisputed. Soon to be 44 years old early in 2010, he got his big break by knocking out an undefeated Felix Trinidad in 2001. Hopkins proceeded to record 20 defenses of the middleweight title before his streak was ended with two razor-thin losses to Jermain Taylor. Hopkins then beat linear light heavyweight champion Antonio Tarver before losing his second divisional title to Joe Calzaghe.

4. Marco Antonio Barrera

Entering the year 2000, Marco Antonio Barrera was considered past his best. But after taking an undefeated Erik Morales to the limit, altering his style from brawler to technician and outclassing an undefeated Prince Naseem Hamed, he never looked better. Barrera went on to win a classic trilogy against Morales.

5. Juan Manuel Marquez

Incorporating more brawling into his scientific approach to boxing, Marquez won the hearts of the Mexican people by nearly getting the best of Manny Pacquiao on two occasions and coming out on top in wars with Marco Antonio Barrera, Joel Casamayor and Juan Diaz.

6. Miguel Cotto

Unlike the other names on this list, Miguel Cotto’s entire career has taken place in the 2000s. And with only two losses, one against a man much higher up on this list, his career has been a steady one highlighted by hard-fought wins against Zab Judah, Shane Mosley and Joshua Clottey.

7. Joe Calzaghe

One of only two undefeated fighters on the list, Joe Calzaghe ended his career in 2008 after racking up 21 successful defenses of the super middleweight title. He beat Bernard Hopkins for the light heavyweight crown but a lack of formidable opponents at 168 pounds and a failure to land fights with top light heavyweights like Roy Jones Jr. – who was far past his best when Calzaghe fought him – keep Joe from a higher rating, but his talent is not questioned.

8. Winky Wright

Winky Wright had a hard time breaking out of anonymity in the 90s but he kept at his craft and carved out his own niche at junior middleweight while awaiting his opportunity. When the time arrived, he came up big with wins over Shane Mosley and Felix Trinidad before dropping decisions to a bigger Bernard Hopkins and the awkward, high volume puncher Paul Williams.

9. Shane Mosley

Coming into the new millennium, Shane Mosley was recognized as the best lightweight in the world. He got his first taste of the big time in 2000 with a win over Oscar De La Hoya and never looked back. Never one to back away from a fight, Mosley has taken on the best the sport has to offer.

10. Wladimir Klitschko

In the wake of Lennox Lewis’ retirement, Wladimir suffered major setbacks but still emerged from one of the more drab eras in heavyweight history as the most skilled and consistent heavyweight in the world. Klitschko seized two of the belts from the fractured heavyweight crown – the closest anyone has come to unifying and giving boxing its first undisputed heavyweight king since Lewis.

Others for Consideration

While many more fighters made their mark on boxing over the last decade, not all of them were able to sustain to the same degree that these 10 did. Oscar De La Hoya, Erik Morales, Kostya Tszyu, Ricky Hatton and Vitali Klitschko all made their case in the 2000s but fell short for various reasons.

De La Hoya participated in more big fights than any fighter before him but suffered five defeats in the decade. Morales competed in classic after classic but failed to rejuvenate his career for the long haul after two losses to rival Barrera. Although he remains the last man to beat Pacquiao, Morales was twice knocked out in rematches and ended his career on a four-loss slide.

140-pound supremacy transitioned from Tszyu’s hands from 2000 to 2005 into Hatton’s hands until 2009, thereby splitting the decade in half and denying either a spot in the list. And though it appeared heavyweight domination was sure to be Vitali’s after coming up short in a brutal battle with Lewis, injuries forced him into a four-year layoff, thereby opening the door for his brother, Wladimir, to climb into the list in his place.