Despite the derision levelled towards crossover fights between boxers and mixed martial artists over the decades, the fact remains that some of the greatest fighters of all time have crossed the divide to do battle in a new trade – often for the entertainment of millions.
Boxing rookies KSI and Faze Temper are a dimension removed from the likes of Claressa Shields, Evander Holyfield and Anderson Silva, but they followed an orthodox path pursued by several sporting icons when they scrapped on January 14.
The latest boxing-MMA crossover could see Tyson Fury take on former UFC champion Francis Ngannou with both fighters seemingly interested in a scrap.
"Francis Ngannou, I know you’re out of contract with the UFC," Fury said when speaking to Radio Rahim. "You want to earn some big boy money? Come see ‘The Gypsy King’ and let’s do a big, big fight for the baddest MF on the planet.
"Let’s kick it up spicy, in a cage, four-ounce gloves under Queensbury [rules] and let’s have a badass referee like ‘Iron’ Mike Tyson. Did I just sell that to the world?"
The origins of modern MMA, combat historians might argue, can be partly attributed to these kinds of fights and the influence of the figures who have been lured to take part in them.
From fierce press conferences and brutal knockouts to risible spectacles and faded legends, we take a look at some of the showdowns to have played out in the name of inter-disciplinary bad blood.
MORE: KSI beats FaZe Temperrr in boxing showdown
Muhammad Ali vs Antonio Inoki (1976)
Considered by some as the direct precursor to modern MMA, this bizarre exhibition boxing draw over 15 farcical rounds pitted Ali in his prime against professional wrestler Antonio Inoki, who spent almost the entire fight on his back, having been granted permission within the rules to perform a technique that involved firing kicks into the air while Ali unsuccessfully beckoned him upwards.
Ali pocketed $6 million and his opponent - and later friend - earned $4m, but the vast sum almost wasn't worth it for the then-WBA, WBC, and The Ring champion: fight promoter Bob Arum revealed that Ali spent weeks in hospital afterwards and almost had to have a leg amputated as a result of blood clots and an infection he suffered because of Inoki's relentless, deceptively expert assault from the floor.
Tim Sylvia vs Ray Mercer (2009)
Former Olympic and WBO heavyweight champion Mercer had challenged the likes of Lennox Lewis, Evander Holyfield and Wladimir Klitschko before stepping up to face two-time UFC heavyweight champion Sylvia in 2009 – a tall order given that the 48-year-old's opponent was 15 years his junior and had a seven-inch height advantage thanks to his 6ft 8in frame.
To his cost, Sylvia also entered the cage at the Adrenaline MMA weighing more than 22 stone, looking predictably ponderous during the nine seconds he lasted before being clobbered conclusively to the floor by the final punch of Mercer's career.
Randy Couture vs James Toney (2010)
At the age of 42 and with his boxing career finally winding down, three-weight world champion Toney signed a contract with the UFC and unwisely took on Randy Couture, a six-time champion of the promotion who was five years his senior and required less than a round to beat him via an arm-triangle choke.
UFC president Dana White insisted afterwards that he had not intended to "hurt the sport of boxing" and defended the decision to sign Toney for what proved to be the powerhouse's first and last MMA fight. Toney later called Couture a "coward" because he claimed his opponent had failed to honour an agreement to meet him in a return boxing match.
I love boxing, but it is ridiculous to assume that the outcome of an MMA fighter vs boxer would be any different to this.
— BR (@hairybads) April 28, 2022
Randy Couture vs James Toney (an all-time boxing great). https://t.co/v3qoLZZSRG pic.twitter.com/BauDoWfQ7I
Valentina Shevchenko vs Nerys Rincon (2011)
Former Muay Thai champion and current UFC flyweight queen Shevchenko was a national amateur boxing champion in 2007, and the Kyrgyz-Peruvian interrupted her MMA career to make her debut in professional pugilism with a unanimous decision victory over Halanna Dos Santos as a 22-year-old in 2010.
'Bullet' knocked out Nerys Rincon in Lima in her only other fully-fledged boxing bout in December 2011, four years before she first appeared in the UFC and seven years prior to beating the equally feared Joanna Jedrzejczyk to win the belt she still holds now.
Holly Holm vs Ronda Rousey (2015)
American Holm had established herself as one of the best female boxers of all time but was given almost no chance by any credible commentators ahead of one of her early MMA fights, taking on long-serving, unbeaten UFC bantamweight champion Ronda Rousey in the promotion's first event in Australia.
Rousey was widely available as a 1/20 odds-on favourite with bookmakers but lost a round for the first time in her career in the opening stanza before being knocked out by a kick to the neck from the southpaw in the second. Holm had caused arguably the greatest MMA upset of all time but lost her three subsequent bouts and never won a belt again, while Rousey left the discipline following defeat to Amanda Nunes when she attempted to regain her former title in her next fight.
Kimbo Slice vs Ken Shamrock (2015)
The late flamboyant actor, YouTube personality, former American footballer and MMA combatant Slice - aka Kevin Anderson - was unbeaten in the seven-fight professional boxing career he built in less than 18 months between 2011 and 2013.
When he returned to the cage after an absence of more than five years in 2015, the former UFC fighter settled a long-standing rivalry with Ken Shamrock - a revered MMA veteran who fought in UFC 1 - by escaping a lightning submission to improbably knock out his opponent in Missouri. UFC commentator and broadcaster Joe Rogan later described the Bellator contest as "fake as f***".
Israel Adesanya vs Lance Bryant (2015)
Current UFC middleweight number one Adesanya was the champion until his defeat to Alex Pereira in November 2022 and also won titles during a seven-year kickboxing career, but the multitalented fighter paused his MMA rise for two years to concentrate on boxing, losing his first bout by decision to Daniel Ammann in the Super 8 Boxing Tournament in 2014.
Adesanya returned to win the tournament twice across five fights in 20 months, twice beating an opponent who had questioned his ability to handle the demands of competing across different disciplines during the same year. "I am trying to make history," Adesanya said before his triumph. "I don't think there is anyone else who has won four major tournaments in a year in kickboxing and boxing."
Conor McGregor vs Floyd Mayweather (2017)
The 50th and final fight of Mayweather's perfect professional career had all the hallmarks of the money-spinning exhibitions he has headlined ever since: an abundance of full-beam tackiness, a maverick opponent not noted primarily for their boxing skills in two-weight UFC champion McGregor and, in the 10th-round victory for 'Money', a result that the modern boxing great could likely have inflicted far earlier, had he desired.
McGregor, who has spoken more recently of his ambition to win a boxing title, landed a few early shots for the cameras in Las Vegas and remains one of the few dance partners for Mayweather able to match the self-mythologising showman's often-tasteless smack talk. Most importantly for two men who tout themselves as master businessmen, the fight was the second-highest grossing boxing match of all time, reportedly bringing in 4.3 million pay-per-view buys and at a total revenue of $396m (£331m).
Still can’t believe we got a Mayweather-McGregor build up and fight lmao
— Connoisseur of Combat (@ConOfCombat) July 12, 2020
Happy 3 year anniversary to this pic.twitter.com/zYUsGgvqkZ
Claressa Shields vs Abigail Montes (2021)
Unsurprisingly, three-weight world champion and current light middleweight titlist Claressa Shields used her striking to salvage victory from the jaws of defeat when she recovered from losing the first two rounds to knock out Brazilian jiu-jitsu brown belt Brittney Elkin on her MMA debut, having signed a three-year deal with the Professional Fighters League.
Shields had a taste of unwanted history when she lost a split decision to unbeaten Montes in her only MMA fight since, suffering her first combat defeat in the process. The irrepressible two-time Olympic gold medalist has, however, become an undisputed boxing champion for a second time since then and gone on to beat Savannah Marshall at London's O2 Arena, where the celebrated rivals became the first female boxers to headline a card at a major UK venue.
Vitor Belfort vs Evander Holyfield (2021)
During a 22-year MMA career in which Belfort challenged Jon Jones and Anderson Silva for UFC titles, the Brazilian bruiser still found room to make his pro boxing debut in 2006, knocking down Josemario Neves three times for a first-round win.
Belfort wasn't necessarily to blame, but there was little to be proud about in his win over Holyfield. The former undisputed cruiserweight and heavyweight champion stepped in at two weeks' notice and, at the age of 58, was battered around the ring on his way to being badly beaten in this exhibition boxing match, which was moved from Los Angeles to Florida after the California Commission refused to sanction it.
Vitor Belfort’s pressure proved to be too much for Evander Holyfield.
— ESPN Ringside (@ESPNRingside) September 12, 2021
(via @OmarESPN) pic.twitter.com/wlR89gCjJC
Anderson Silva vs Jake Paul (2022)
Silva is rightly serenaded as one of the greatest UFC fighters ever thanks to his record-setting reign as middleweight champion, and boxing was a first love he initially interspersed around MMA with a defeat in 1998 and victory over future WBC middleweight king Julio Cesar Chavez Jr in 2005.
With his final UFC fight probably behind him and at the age of 46, Silva recorded successive boxing wins in 2021 over Chavez Jr and another former champion in Tito Ortiz. He then beat fellow MMA veteran Bruno Machado on the undercard of a Floyd Mayweather exhibition bout in 2022, only to suffer a unanimous decision defeat at the hands of 25-year-old YouTuber-turned-fighter Jake Paul in Arizona later that year.
