Is McGregor really retiring at 27? Five other sports stars who called it quits in their prime
The supposed 'retirement' of Conor McGregor would be a huge shock for many reasons, not least of which that the Notorious would be walking away from the sport at the peak of his physical power.
Sure, McGregor lost for the first time in the UFC to Nate Diaz at UFC 196, but with the Dubliner not set to turn 28 until after their proposed July rematch, he had plenty of time left to build a lasting sporting legacy.
Most fighters only enter their prime in their late 20s, as they are still young enough not to have lost any of their reflexes but old enough to have absorbed crucial lessons on how to combat different styles.
But if McGregor truly does mean to retire immediately, he won't be the first sports star to walk away even though everything was pointing to them being able to continue their dominance.
Here are five athletes who opted to call time on their careers prematurely.
Tennis is an unusual sport in that players tend to peak in their early 20s and it is not uncommon for someone to dominate in the early part of their career before fading into relative obscurity as they enter their 30s.
Perhaps 11-time Grand Slam-winner Bjorn Borg was trying to preemptively avoid that by hanging up his racket at the outrageously young age of 26. It is not as if the Swede showed many signs of wilting - in his final full year on tour he won the French Open and reached the final of Wimbledon and the US Open.
Borg retired with six French Open titles and five Wimbledon crowns but the knowledge that he could have achieved more seemed to eat away at him, because he attempted a comeback at 34 in 1991.
He failed to win a single match over the next two years before retiring for good.
Cantona bounced around six clubs in France before finding a proper home in England with Manchester United - with a successful title-winning season with Leeds along the way.
The mercurial Frenchman led the Red Devils to Premier League glory during four of his five seasons in Manchester while also adding two FA Cup medals to his trophy cabinet. But following the 1996-97 season, Cantona shockingly decided to retire from football at 30, despite scoring 15 goals in all competitions that year.
In a 2004 interview Cantona revealed that he sometimes feels he quit football too young, but that he didn't have the passion to devote himself to the game any longer. At least he remained committed to entertaining us in retirement.
Ella's career in international rugby was brief but he enjoys a lasting legacy as part of Australia's 1984 Grand Slam team, who beat Wales, Ireland, England and Scotland on a northern hemisphere tour.
Ella was the dynamic play-making out-half, more focused on creating space for team-mates than kicking the ball to the corner. The Australian led a backline featuring David Campese and Michael Lynagh, and it was thought that the team could potentially dominate world rugby until Ella sensationally retired at just 25 after the 1984 tour.
In his absence, Australia still won the World Cup in 1991 but rugby fans still wonder how good that team could have been had Ella stuck around.
Despite being voted to the NFL Pro Bowl every season of his ten-year career, running back Barry Sanders decided to retire at 31 - playing for the Detroit Lions will do that to you.
Although Sanders was one of the league's best players throughout his time in the NFL - he won the MVP award in 1991 - the Lions never made it to the Super Bowl.
So keen was Sanders to cut ties with his underachieving team, he agreed to pay back the signing bonus on his last contract just so he would no longer have to play for them.
Not only does Marciano have one of the greatest names in boxing history but he also enjoys the most perfect record. The undefeated heavyweight finished his career at an unblemished 49-0, a record that Floyd Mayweather has since joined him on.
The Brockton Blockbuster won the world title at 29 after beating Jersey Joe Walcott before defending his belt six times. After beating Archie Moore at Yankee Stadium in 1955, Marciano hung up his gloves at age 32.
Marciano could have fought on but the only time he came close to a comeback was when he resumed training in 1959 for a bout with champion Ingemar Johansson... but after a month of working his way back into shape, the former champions thought he might be better off retired.