Manny Pacquiao announced his retirement on Wednesday, officially bringing an end to an astonishing 26-year career in which the Filipino won world titles across eight distinct weight classes.
The 42-year-old, who now narrows his focus towards running for Philippines president next year, exits the sport as one of the all-time greats, winning 12 world titles throughout his 72 fights, of which he won 62, lost eight and drew two.
The future Hall of Famer, who won his first world title at the age of just 19, became renowned for accepting any and every challenge, while taking on the best in the business seemingly regardless of their weight.
But where does he rank among the pound-for-pound best boxers to grace the ring in the 21st century?
Sportsmail attempts to answer the question below, but there is a slight caveat: This is not the best fighter to have entered the ring this century - this list analyses the accomplishments achieved in the given timeframe.
Floyd Mayweather (left) and Manny Pacquiao (right) top Sportsmail's pound-for-pound stars
We start with Gennady Golovkin, who is one of the best middleweights ever to grace the sport.
The 39-year-old won his first strap in his 19th outing, claiming the WBA interim middleweight belt against Milton Nunez in just his second bout outside of Germany, which became a second home during the early stages of his career.
Golovkin carries extraordinary power and continued to march through the middleweight division as he picked up the IBO strap just three fights later.
He memorably stopped Britain's Martin Murray in the 11th round of their 2015 bout, before knocking out David Lemieux just eight months later to unify the division as he claimed the Canadian's IBF strap.
Golovkin continued to show is fearsome prowess as he handed Kell Brook the first defeat of his career in 2016 with a brutal fifth-round stoppage win, though his opponent did jump two weight classes for the challenge.
Gennady Golovkin fell marginally short in his epic double-header against Canelo Alvarez
His points win over Daniel Jacobs, though ending a run of 23-straight knockouts, provided a reminder that Golovkin does indeed possess an elite-level skillset, not just his brute force.
Then came the decisive moment in Golovkin's career, as he and Canelo Alvarez shared a controversial draw in their 2017 outing. Though the Mexican finished the fight the stronger, many to this day believe it was Golovkin who won what was a closely-contested affair.
But in the rematch - which followed a stoppage win over Vanes Martirosyan - GGG was defeated via majority decision, with Canelo claiming the WBA and WBC straps.
Golovkin's reign as middleweight champion was over, though he did quickly regain his former IBF strap with a 2019 win over Sergiy Derevyanchenko.
Now, there are reports he will take on WBA titleholder Ryota Murata on December 31 as he bids to unify the division once more.
Record: 41 wins, 1 loss, 1 draw (36 KOs)
9) Oleksandr UsykNext up is Oleksandr Usyk, who cemented his place in this list with a truly phenomenal performance against Anthony Joshua last weekend.
The Ukrainian made the switch to professional boxing after a stellar amateur career, in which he claimed gold at the London 2012 Olympics and won a staggering 350 bouts.
With experience aplenty, Usyk swiftly rose through the cruiserweight ranks, winning a world title after just 10 fights as he defeated Krzysztof Glowacki with ease.
And just five fights later, Usyk became the first-ever undisputed cruiserweight champion in the four-belt era, as he convincingly defeated Murat Gassiev to win the World Boxing Super Series.
Oleksandr Usyk outclassed Anthony Joshua to become unified heavyweight world champion
After defending his belts with another highly impressive performance against an in-form Tony Bellew, Usyk made the step to heavyweight, where he has only furthered his already-magnificent reputation.
He found his feet as a heavyweight in less-than convincing wins over Chazz Witherspoon and Derek Chisora, but it was against Joshua where the 34-year-old truly showed his credentials.
Fighting on away turf, a familiar trend throughout his career, Usyk silenced the 70,000 in attendance at the Tottenham Hotspur Stadium, with his ingenious lateral movement and unwavering stamina proving too much for the WBA, WBO and IBF champion.
The pair are set to go to battle once more in the rematch, which will take place early next year. The Ukrainian has already outlined his intentions to become undisputed champion once more should he prevail again.
If Usyk is to eventually beat one of Tyson Fury or Deontay Wilder for all of the belts, he will no doubt rise significantly on this list.
Record: 19 wins, 0 losses, 0 draws (13 KOs)
8) Marco Antonio BarreraComing in at No 8 is Marco Antonio Barrera, who was inducted into the International Boxing Hall of Fame in 2017.
Known as the 'Baby-Faced Assassin', the three-division world champion retired with a record of 67 wins, seven losses and no draws, with 44 of his victories coming by way of knockout.
It's primarily his performances in the early 2000s that earn Barrera a place on this list, having beaten the likes of British legend Naseem Hamed, alongside two scalps over Erik Morales in an epic trilogy.
Morales, who won the first bout between the pair, subsequently described Barrera as the biggest puncher he had ever faced in the ring, while their first and third bouts were labeled the 'Fights of the Year' by The Ring Magazine.
Though claiming a number of eye-catching scalps throughout his career, Barrera will always be remembered for his pair of defeats to Pacquiao, the first by TKO in 2003 and the second by unanimous decision in 2007.
Marco Antonio Barrera (right) was inducted into the International Hall of Fame in 2017
But he will also be remembered for his ability to bounce back in defeat. Having fallen to back-to-back losses to Junior Jones in 1997, the Mexican was largely written off - a mistake given he won his next 14 of 16 bouts.
And after losing to Pacquiao in 2003, he bounced back to reign for over two years as WBC super-featherweight champion.
Barrera would retire with a record of 21-4 in championship fights across a career lasting over 20 years.
Remarkably, Barrera, 47, is set to return to the ring for the first time in over a decade as he takes on 41-year-old Daniel Ponce De Leon in a six-round welterweight clash on November 20.
Record: 67 wins, 7 losses, 0 draws (44 KOs)
7) Nonito Donaire'The king has returned,' Nonito Donaire said as he broke his own record as the oldest bantamweight in history to win a world title.
At 38 years old, Donaire delivered an emphatic performance to topple France's Nordine Oubaali and become a three-time bantamweight champion earlier in May this year.
It came after legendary fighter lost to one of the current pound-for-pound stars Naoya Inoue in their 2019 World Boxing Super Series match-up, handing over his WBA title in the process.
The fight one was of epic proportions, however, as Donaire delivered a trademark left-hook that saw Inoue suffer an orbital fracture and left him with double vision throughout the contest.
Inoue battled hard and dropped Donaire in the 11th round, before claiming a unanimous decision victory via scores of 116-111, 117-109 and 114-113.
Nonito Donaire broke his own record as the oldest ever bantamweight world champion
Though losing the fight, it was another reminder of Donaire's extraordinary talent, which was evident all the way back in 2007 when he destroyed Vic Darchinyan in five rounds to win his maiden world title.
His performance in the fight also proved to Donaire himself that he could still perform at the highest level.
After beating Oubaali, he said: 'What I learned from the Inoue fight is that I'm back. I can still compete at this level. The whole time I was not fighting, I was learning. I'm ready for the next one.'
So the journey continues for the four-weight world champion, who has an extraordinary 41 wins on his 47-fight record. He's already booked his place in the Hall of Fame, but how much further he can take his career remains to be seen.
Record: 41 wins, 6 losses, 0 draws (27 KOs)
6) Roman GonzalezThough falling to a controversial defeat in his most recent encounter, Roman Gonzalez has to be included in this list.
Gonzalez was handed the third loss of his 53-fight career in March this year, as Juan Franciso Estrada avenged his 2012 defeat to unify he WBC and WBA super-flyweight titles. Gonzalez finished the fight the stronger of the two, but it wasn't to be for the great champion this time round.
The 34-year-old is the only Nicaraguan to become a four-division champion, doing so in 2016 as he defeated Carlos Cuadras via unanimous decision to claim the WBC super-flyweight belt.
Roman Gonzalez is the only Nicaraguan ever to become a four-division world champion
It added to his titles held at flyweight, light-flyweight and mininumweight, moving to 46-0 at the time and then holding the title as perhaps the best pound-for-pound fighter on the planet.
Immediately after his historic win over Cuadras, Gonzalez did fall to back-to-back defeats to Wisaksil Wangek. However, he rolled back the years once more by defeating Britain's then longest serving champion Kal Yafai to claim his WBA world super-flyweight title.
Chocalito will reportedly complete his trilogy against Estrada later this year, after their proposed October bout was postponed as Gonzalez tested positive for coronavirus.
Record: 50 wins, 3 losses, 0 draws (41 KOs)
5) Juan
