By Rick Reeno

In shocking fashion, Floyd Mayweather Jr, regarded as the best fighter in the sport, announced his retirement from boxing on Friday. The public debate will now begin as to who is the best pound-for-pound fighter in the sport.

Depending on the list, Manny Pacquiao (WBC super featherweight champion, Ring champion) and Joe Calzaghe (undisputed super middleweight champion, Ring light heavyweight champion) are usually holding court in the number-two position, with Mayweather at the head of the pack.

Who should be the new pound-for-pound best? Both fighters will have their supporters and their critics.

Pacquiao began his career at 106-pounds and won titles at 112, 122 and 130. On June 28, he tries to capture a fourth world title in a fourth weight class when he challenges WBC lightweight champion David Diaz. Pacquiao is almost never in a dull fight. He fought, and beat, some of the the best pound-for-pound fighters that our era had to offer.

Calzaghe has been a career super middleweight. After 44 fights as a pro, he finally moved up in weight to the light heavyweight division in April to decision Bernard Hopkins. During the last few years, Calzaghe gained a mountain of recogniztion with impressive wins over Jeff Lacy and Mikkel Kessler.

Examining both fighters in a few key areas, it doesn't make the decision any easier. It all depends on what you like in a fighter and what impresses you the most.

In terms of records, Pacquiao has three losses and two draws. Two of the losses (both by knockout) were at the early stage of his career when he was killing himself to make weight. He's been hit by much bigger punchers since then and his chin has held up fine. The third loss, to Erik Morales in 2005, was legit. Calzaghe has a perfect record of 45 wins with no losses, unbeaten since 1993 and defended his title 21-times.

Record Nod -Calzaghe

In terms of resume, Pacquiao has beaten a who's who of Mexican warriors, including Marco Antonio Barrera (twice), Erik Morales (twice), Oscar Larios and Juan Manuel Marquez. Calzaghe's biggest (or most publicized) wins have come in the last 25-months. He dominated Lacy (undefeated) in 2006, won a tough fight with Kessler (undefeated) in 2007 and won a close split-decision over Bernard Hopkins in April of 2008.

Between the two of them, Pacquiao's has beaten three of the best fighters to ever come out of Mexico, and all three, Morales, Barrera and Marquez, are easily hall of fame bound. Lacy has never been the same since the loss to Calzaghe, and most have written him off as an overhyped product. Kessler has yet to win a career defining fight and Hopkins was 43-years-old and taking part in the final lap of his career. The second most recognizable name (and probably the second best fighter) on Calzaghe's record is Chris Eubank, who was also at the end of his rope at the time of the loss. Kessler, 29, is still a young fighter. There is plenty of time for him to regroup and become a major force in the sport.

Resume Nod - Pacquiao

In terms of excitement, Pacquiao's "kill or be killed" style blows away Calzaghe in most fights. There have been very few lackluster Pacquiao bouts over the last few years. Calzaghe's slapping style and inability to produce big knockouts have not made him a big favorite among fight fans in America. In his last eight fights, Calzaghe has only stopped two opponents.

Excitement Nod - Pacquiao

In terms of being a draw, both fighters can pack the house in their respective countries, but Pacquiao is not only the biggest boxing star of his country - he's the biggest star period. Hatton is a bigger draw than Calzaghe in the UK and America. No Filipino comes close to matching Pacquiao's star power in any country. Some may argue that most of Pacquiao's attendance numbers are made up of local Filipino fans, but quite a few, including high ranking officials, fly in as well. Calzaghe's American debut against Hopkins was not the box office hit that many expected. The tickets were a tough sell.

Star Power Nod - Pacquiao

In terms of ability, Calzaghe is significantly more polished. He may not have the explosive style of Pacquiao, but he's a much better boxer and has the ability to adapt to his opponent and switch his style as the fight progresses. Pacquiao is still an unfinished product. Calzaghe, 36, learned as he went along. Pacquiao is only 29-years-old. He still has plenty of time to become a more complete fighter.

Ability Nod - Calzaghe

In terms of accomplishments, it's Calzaghe's unbeaten fifteen-year career, eleven-years as an unbeaten champion and 21-title defenses vs. Pacquiao's ability to capture three world titles in three weight classes after starting his career at 106-pounds. While Pacquiao may have faced more notable opponents, it takes a world of dedication to defend your title 21-times regardless of the opposition.

Accomplishments Nod - Calzaghe

If I was put on the spot, I would probably place Calzaghe above Pacquiao. BoxingScene.com's Cliff Rold, who manages our pound-for-pound list, would list Pacquiao above Calzaghe. I only have Calzaghe slightly ahead. Depending on how well Pacquiao performs against Diaz, he could very well end up above Calzaghe on my list.