The more Kamaru Usman continues to stockpile title defenses on his march toward potentially eclipsing Georges St-Pierre as the greatest welterweight in UFC history, the number of viable opponents he hasn't yet beaten continues to dwindle.
Usman defended his 170-pound crown for the fifth time at UFC 268 in his second straight rematch by edging Colby Covington via unanimous decision. At 34, "The Nigerian Nightmare" finds himself without peer at the moment atop the sport's pound-for-pound list and could make a run at the history books depending upon how much longer he continues to fight.
Although Usman hasn't necessarily teased that a mic drop exit is imminent, recent abrupt retirements by former champions Khabib Nurmagomedov and Henry Cejudo suggest we are in the midst of a trend. And outside of a rising yet still raw Khamzat Chimaev, there isn't a slam dunk next choice for a fresh opponent considering Usman has already beaten Leon Edwards, and both Vicente Luque and Michael Chiesa fail to offer the champion a marketable reason to stay so active.
Regardless of what happens next, Usman's incredible evolution over his last four fights under new coach Trevor Wittman has him on the verge of some rarified history. Usman is one win shy of tying Anderson Silva's promotional record of 16 straight victories. And even though he is still four title defenses away from equaling GSP's welterweight mark, the dominance behind his current win streak make it so Usman might not need to eclipse said mark to fully cement his legacy.
Can't get enough boxing and MMA? Get the latest in the world of combat sports from two of the best in the business. Subscribe to Morning Kombat with Luke Thomas and Brian Campbell for the best analysis and in-depth news.
Not only is Usman unbeaten in 15 trips to the Octagon, he hasn't be challenged or pushed by anyone not named Covington, whom he has now beaten twice in close fights. Usman has also won 19 consecutive fights overall since a loss in his second pro outing and enjoys a level of sustained dominance even St-Pierre couldn't match.
Should Usman continue on in his winning ways, admission into the upper room of all-time great fighters with a case to be called the G.O.A.T. seems inevitable. Already a dominant wrestler, Usman has proved in 2021 with stoppage wins in title defenses over Gilbert Burns and Jorge Masvidal that he's now just as dangerous on his feet.
And then there's the debate over his perfect takedown defense record, which stands alone atop the UFC record books. Some have argued that Covington came incredibly close to scoring one at UFC 268, yet it remains moot to the overall point.
With Nurmagomedov's recent retirement and the combination of Jon Jones' decline and inactivity, Usman currently stands in a class of his own as the best male fighter in the sport -- and, somehow, he's only getting better.
For CBS Sports' updated divisional rankings,.
Men's pound-for-pound rankings
| 1. Kamaru Usman||Welterweight champion||20-1||--|
|The recent evolution of "The Nigerian Nightmare" as a striker is something to behold under coach Trevor Wittman. Usman's close victory over Colby Covington in their rematch at UFC 268 was further proof of how efficiently the champ has cleaned out the division.|
|2. Israel Adesanya||Middleweight champion||21-1||--|
|A hiccup at light heavyweight in March while attempting to become a two-division champion did nothing to question whether Adesanya is still the best 185-pound fighter in the world today. His UFC 263 shutout of Marvin Vettori in their rematch was masterful, setting the stage for another with former champion Robert Whittaker.|
|3. Alexander Volkanovski||Featherweight champion||23-1||--|
|The wizard of 145 pounds appeared to quiet any remaining skeptics by how fiercely he defended his title against Brian Ortega at UFC 266. Unbeaten in 10 trips to the Octagon, Volkanovski is on his way toward creating a historically relevant career resume at featherweight.|
|4. Francis Ngannou||Heavyweight champion||16-3||--|
|How do you properly frame how scary and dangerous this man is? If Ngannou's knockout streak hasn't fully convinced you, the evolution shown during his rematch with Stipe Miocic to seize the title should be enough. The 35-year-old is improving at a terrifying rate. He has a date with interim champ Ciryl Gane set for January.|
|5. Petr Yan||Interim bantamweight champion||16-2||--|
|Status lost in his DQ defeat to Aljamain Sterling that cost Yan his 135-pound title in a fight he was winning was completely restored at UFC 267. Yan outpointed a game Cory Sandhagen in a thriller to capture the interim title, setting up a Sterling rematch and renewed claim as bantamweight's best.|
|6. Dustin Poirier||Lightweight||28-6 (1 NC)||--|
|After choosing a pair of high-profile rematches against Conor McGregor over fighting for the lightweight title, Poirier will finally get his chance in December to prove he's the best lightweight of the post-Khabib Nurmagomedov era. Defending champion Charles Oliveira awaits him.|
|7. Charles Oliveira||Lightweight champion||31-8 (1 NC)||--|
|Nine straight victories culminated with the Brazilian stopping Michael Chandler to capture the vacant lightweight crown at UFC 262. Oliveira is the most prolific finisher in UFC history and is expected to make his first title defense against Dustin Poirier at UFC 269.|
|8. Max Holloway||Featherweight||23-6||--|
|In a thrilling November victory over a refreshed Yair Rodriguez, Holloway showcased everything that makes him great over five rounds, from an iron chin to championship-level adjustments. If a trilogy against Volkanovski isn't next, "Blessed" has shown huge interest in rematching Conor McGregor.|
|9. Robert Whittaker||Middleweight||23-5||--|
|A three-fight win streak, all against elite competition, has the former middleweight champion set for an early 2022 rematch against Adesanya. Whittaker has used the time since his 2019 TKO loss to rebuild himself from a technical standpoint and appears as dangerous as ever.|
|10. Justin Gaethje||Lightweight||23-3|
|The former interim lightweight champion just might be on the doorstep of fighting for the full title for a second time following his UFC 268 win over Michael Chandler. Gaethje is 5-1 since altering his style just a bit from full-time brawler to tactical finisher.|
Dropped out: Brandon Moreno
Just missed: Moreno, Cyril Gane, Aljamain Sterling, TJ Dillashaw, Glover Teixeira
Women's pound-for-pound rankings
|1. Amanda Nunes||Bantamweight/Featherweight champion||20-4||--|
First-time parenthood did nothing to slow "The Lioness" in her dominant finish of Megan Anderson in March to defend her 145-pound title. Nunes moves back down to bantamweight in December to welcome challenger Julianna Pena.
|2. Valentina Shevchenko||Flyweight champion||22-3||--|
|Despite holding a pair of close defeats to Nunes at bantamweight, Shevchenko is making a run of her own toward P4P greatness following a move down to 125 pounds. Six dominant title defenses have followed, including a TKO of Lauren Murphy at UFC 266.|
|3. Rose Namajunas||Strawweight champion||11-4||--|
|A split-decision win over former champion Weili Zhang in their UFC 268 rematch has Namajunas one step closer to cementing status as the greatest female 115-pound fighter in UFC history. Up next is likely yet another rematch against inaugural titleholder Carla Esparza.|
|4. Carla Esparza||Strawweight||18-6|
|Five straight wins and a dominant finish of contender Yan Xiaonan has the UFC's first women's champion at 115 pounds on the verge of a possible shot at regaining her crown. "The Cookie Monster" is currently the most dangerous and confident version of herself to date at 33 and riding a ton of momentum.|
|5. Carla Esparza||Strawweight||21-2|
|Despite a razor-thin loss to Namajunas in their title rematch, Zhang showed just how tough she was in rebounding from a first-round knockout loss. The first Chinese-born UFC champion remains among the elite although her road back to a title shot remains uncertain.|
Dropped out: None
Just missed: Jessica Andrade, Germaine de Randamie, Holly Holm, Marina Rodriguez, Katlyn Chookagian