Since the inception of sport, one opponent remains undefeated for any athlete - regardless of ability, competitive spirit or resilience: Father Time.
It could be argued that LeBron James has put up the toughest fight yet, having been the dominant force in the NBA for the best part of two decades. But after the 36-year-old's team, the Los Angeles Lakers, were knocked out in the first round of this season's play-offs, there are those who've been left wondering: Is this the end of an era?
"He's been doing this for half of his life at the highest level - and a lot of people won't understand what it takes not only to compete but remain at that level," Myles Hesson, the Great Britain men's basketball captain, said.
"I wouldn't say it's the end of an era - more like the changing of an era. I think we've come to a point where he needs help, maybe more help than he needed before." James is widely considered one of the greatest basketball players of all time - if not the greatest.
Many players, coaches, commentators and fans often agree it's a direct toss-up between James and Chicago Bulls legend Michael Jordan. James has won the NBA Championship four times - with three different teams - a feat many see as testament to his ability to transform the fortune of a franchise.
During his 18 seasons in the NBA, he has led his team to the play-offs on 15 occasions.
Before the recent 113-100 loss to the Phoenix Suns - who won their best-of-seven series 4-2 - he had never failed to make it past the first round.
James, originally drafted as the first overall pick by the Cleveland Cavaliers in 2003, has been described as one of the most durable athletes of all time - largely enjoying an injury-free career. While there may be some luck involved, he also reportedly spends significant amounts of money each year on nutrition, conditioning and recovery techniques.
But Ryan Richards, a Britain-born player drafted by the San Antonio Spurs in 2010, who is now with Petro de Luanda in the NBA affiliated Basketball Africa League (BAL), wonders how much longer James will be at the very top.
"Last night I was expecting vintage LeBron - but it's the age - Father Time is coming," Richards said. "I believe he went into last night's game believing he could win it, you know, and activate 'Play-off LeBron mode' but things just didn't go his way.
"You can't take away the greatness because I think he's the smartest player to ever play the game but I think he realises the game is changing." In a season shortened from 82 to 72 games because of coronavirus restrictions, James missed more than 25 matches with an ankle injury.
And before the start of the play-offs, he told reporters he didn't expect to 100% fit again before the end of the season. This season saw him record a career low points-per-game average of 22.3. At times, he has resorted to long-range shooting, with fewer of his energy-sapping bursts to the basket.
"He still looks amazing and those numbers are still insane but I think there need to be changes," Richards said. "I think the Lakers will use the summer to bring in another big name to help out. There's talk he wants to partner up with Stephen Curry or maybe they'll go for someone like Russell Westbrook.
"I think he needs another star - someone he can lean on. I personally know players who've played with LeBron and he kills your own confidence because he's so great. You have to be ready like a microwave scorer - come in hot and impact the game - play a role for six months and be part of the LeBron show."
With a whole summer to recover and recuperate, James could yet come back next season and prove the doubters wrong. It has been suggested that James - who has always said he wants to play for as long as he can - could stay in the NBA for another two years.
At that point, his son - LeBron 'Bronny' James Jr - would be eligible to join the league. James has put the Lakers' early play-off exit down to their injury problems this year: star forward Anthony Davis missed half the season and limped out after five minutes of the decisive defeat by the Suns.
"We never got an opportunity to see our full team," James said. "We could never fully get into a rhythm." The strain of Covid-19 protocols had an effect too. "From the moment we entered the bubble to today, it's been draining," James said. "Mentally, spiritually, emotionally draining.
"Every team has to deal with it, obviously, but with us and Miami going long-haul in the bubble and coming back on short notice, it's been very draining." Hesson, who plays for Elan Chalon in France's LNB Pro A, believes James will make sure he quits at the right time.
"It's a personal thing for him - he'll know when it's time to hang it up," Hesson said. "I personally still watch him play even when he's not on top form just to see how his basketball mind affects and makes others around him better players."
But if James' star is fading, Hesson says the NBA is in good shape when it comes to finding faces to continue to excite fans for years to come. "I don't think there's one face right now," he said. "I think there are a few guys leading their teams in different ways.
"You've got Giannis Antetokounmpo, Devin Booker, Luka Doncic. Kevin Durant is doing his thing. I kind of like it like this. It's more of an even playing field, where one team or player isn't dominating."