Floyd Mayweather has won all 43 of his professional bouts and it appears increasingly likely that he'll retire with a perfect record.
Though it's exceedingly rare, Mayweather is not the first to go undefeated. Surprisingly, the majority of fighters who retired with a perfect record aren't all that highly regarded.
The list would be significantly better if it included Ricardo Lopez, the great Mexican champion who retired with a 51-0-1 record and 38 knockouts. Only a 1998 draw with Rosendo Alvarez in a title unification bout kept Lopez from being perfect.
Floyd Mayweather Jr. loves his money. (Getty)
Of those who ended their careers with no losses and no draws, the best, and by far the most well known, is the great heavyweight champion Rocky Marciano. The "Brockton Blockbuster" retired at his peak at age 32 in 1955 with a 49-0 record and 43 knockouts.
Marciano scored wins over legends like Archie Moore, Ezzard Charles, Joe Walcott and the great Joe Louis.
Super middleweight Joe Calzaghe retired in 2009 with a 46-0 and 32 knockouts, finishing his career with wins over veteran Bernard Hopkins and Roy Jones Jr. in 2008.
The late Edwin Valero, who died in jail in 2010, had the most perfect record of any fighter ever. Valero was 27-0 with 27 knockouts, including 19 in the first round and two more in the second round.
Veteran Harry Simon, who held super welterweight and middleweight titles, remains somewhat active at 41 with a 27-0 record and 20 knockouts. He didn't fight at all from 2003 through 2006. He fought once in 2007, twice in 2010 and most recently fought in June.
[Also: One-handed boxer wins professional debut]
Though Simon was a quality fighter in his day, with wins over Winky Wright and Hacine Cherifi, among others, he is hardly considered an all-time great. Nor is Sven Ottke, who retired in 2004 with a 34-0 record and six knockouts.
There have been others, none of whom is regarded by boxing historians as exceptional.
When boxing cognescenti speak of the greatest fighters of all-time, the names that often come up are Sugar Ray Robinson and Henry Armstrong. Robinson lost 19 times and Armstrong dropped 21, but there aren't any fighters remotely close to them in the all-time ratings.
If Mayweather does finish unbeaten – and given the few number of bouts he has left, that's likely – he'll vie with Marciano and Calzaghe for the honor of the greatest unbeaten, untied fighter in boxing history.
Nothing he might possibly do in the remainder of his career, though, could help Mayweather to remotely challenge Robinson or Armstrong for their spots as the all-time greatest fighters.
With that, here are the latest Yahoo! Sports boxing top 10 rankings:
Mayweather
Points: 348 (28 of 36 first-place votes)
Record: 43-0 (26 KOs)
Title: WBA super welterweight champion
Last outing: W12 over Miguel Cotto on May 5
Previous ranking: 1
Up next:Nothing scheduled
Analysis:Still has yet to indicate plans for resumption of career
WardPoints: 296 (2 of 36 first-place votes)
Record: 26-0 (14 KOs)
Title: WBA, WBC super middleweight champion
Last outing: TKO 10 Chad Dawson on Sept. 8
Previous ranking: 2
Up next: TBA
Analysis:In talks for January bout with Kelly Pavlik
Pacquiao3. Manny PacquiaoPoints: 288 (6 of 36 first-place votes)
Record: 54-4-2 (38 KOs)
Title: None
Last outing: L12 to No. 8 Timothy Bradley
Previous ranking: 3
Up next:Dec. 8 vs. No. 5 Juan Manuel Marquez
Analysis:Vows he will knock out Marquez, which he desperately needs
Martinez4. Sergio Martinez
Points: 263
Record: 50-2-2 (28 KOs)
Title: WBC middleweight champion
Last outing: W12 Julio Cesar Chavez Jr. on Sept. 15
Previous ranking: 4
Up next: TBA
Analysis: Will be off while knee, hand injuries heal
DonairePoints: 199
Record: 30-1 (19 KOs)
Title: IBF, WBO super bantamweight champion
Last outing: TKO9 over Toshiaki Nishioka on Oct. 13
Previous ranking: 6
Up next: Nothing scheduled
Analysis: May meet Jorge Arce
Marquez6. Juan Manuel MarquezPoints: 184
Record: 54-6-1 (39 KOs)
Title: Interim WBO super lightweight champion
Last outing: W12 Sergey Fedchenko on April 14
Previous ranking: 5
Up next: Dec. 8 vs. No. 3 Manny Pacquiao
Analysis: A convincing win over Pacquiao is his aim
W. KlitschkoPoints: 120
Record: 58-3 (51 KOs)
Title:IBF, WBA, WBO heavyweight champion
Last outing: TKO6 over Tony Thompson on July 7
Previous ranking: 7
Up next: Nov. 10 vs. Mariusz Wach
Analysis: Will be his first fight since 2004 without trainer Emanuel Steward
Bradley
Points: 105
Record: 29-0 (12 KOs)
Title: WBO welterweight champion
Last outing: W12 over No. 3 Manny Pacquiao on June 9
Previous ranking: 8
Up next: TBA
Analysis:Oddly, strangely quiet
V. KlitschkoPoints: 69
Record: 45-2 (41 KOs)
Title: WBC heavyweight champion
Last outing: TKO 4 over Manuel Charr on Sept. 8
Previous ranking: 9
Up next:TBA
Analysis: Still dominant at age 41
FrochPoints: 43
Record: 29-2 (21 Kos)
Title: IBF super middleweight champion
Last outing: TKO5 Lucian Bute on May 26
Previous ranking: 10
Up next: Title defense vs. Yusef Mack on Nov. 17
Analysis: Continues to fight, and beat, highly ranked opponents
Others receiving votes: Miguel Cotto, 30; Anselmo Moreno, 13; Chris John, 7; Roman Gonzalez, 5; Guillermo Rigondeaux, 3; Canelo Alvarez, 2; Adrian Broner, 2; Gennady Golovkin, 2; Abner Mares, 2; Brandon Rios, 1.
Voting panel: Raul Alzaga, Primera Hoya; Al Bernstein, Showtime; Ron Borges, Boston Herald; Damian Calhoun, Orange County Register; Brian Campbell, ESPN.com; Scott Christ, Bad Left Hook.com; Steve Cofield, ESPN Radio 1100; Mike Coppinger, RingTV.com; Jake Donovan, BoxingScene.com; Andrew Eisele, About.com; Steve Farhood, Showtime; Thomas Gerbasi, BoxingScene.com; Nick Giongco, Manila Bulletin; Carlos Gonzalez, Primera Hora; Randy Gordon, Sirius/XM; Lee Groves, Ring Magazine; Rafael Hernandez Brito, Univision; Keith Idec, The Record; Kevin Iole, Yahoo! Sports; Max Kellerman, HBO; Scott Mallon, Boxing Digest; Ryan Maquinana, Comcast Sports Net/Bay Area; Rich Marotta, Fox Sports; David Mayo, MLive.com; Franklin McNeil, ESPN.com; Gunnar Meinhardt, Die Welt; Marty Mulcahey, MaxBoxing.com; Kieran Mulvaney, Reuters; Santos Perez, Miami Herald; Martin Rogers, Yahoo! Sports; Cliff Rold, BoxingScene.com; Lem Satterfield, RingTV.com; Don Steinberg, Wall Street Journal; T.K. Stewart, RingTV.com; Dave Weinberg, Press of Atlantic City. Other popular content on the Yahoo! network:• Y! News: Hurricane Sandy bears down on East (live blog)
• Giants ride eclectic cast to World Series title | Photos
• Michael Silver: Put Peyton Manning on early MVP candidate list
• Notre Dame leaps into the top three of the BCS Standings