More than two decades after first competing in an Olympics game, Steven Lopez's age finally caught up to him.
Lopez, a 37-year-old taekwondo legend who has won two gold medals, won his first match in Rio in the 80kg weight class on Friday against a man more than a decade his junior, but couldn't pull off the feat twice. After beating 24-year-old Albert Gaun of Russia in the first round, he lost in the quarterfinals to 25-year-old Lutalo Muhammad of Great Britain.
Muhammad jumped out to a 4-1 lead in the first period, then piled it on in the fourth period for a 9-2 victory.
Lopez, who won the gold medal in the 2004 and 2008 Olympics, will meet Australia's Hayder Shkara's the men's 80 KG repechage Friday night.
Lopez opened the Rio Olympics by beating a Russian fighter more than a decade younger than him. Lopez beat Albert Gaun, ranked No. 4 in the world entering the Games, 7-4 on Friday to advance to the quarterfinals.
Gaun opened the scoring with a power punch in the first round, but Lopez took a commanding lead in the second period after landing a spin kick and two blows to the body.
At 37, Lopez is the most acclaimed fighter in the sport and dominated the Korean martial art for more than a decade, winning a record five world championship titles.
Lopez won Olympic gold medals in 2000 and 2004 and took home a bronze in 2008. But at the London 2012 games, he was knocked out in the first round after breaking a leg shortly before the Olympics.
Ahead of Rio, Lopez said his misfortune in London adds a bit of extra motivation.
"I can accept defeat if the guy is just better than me that day," he told The Associated Press. "But to not be able to go out there and perform at my best [in 2012] was something that was very hard for me to stomach and one of the reasons why I went on to try to make the Olympic team in 2016."
Still, a lot has changed since Lopez started taekwondo, a martial art characterized by its aerial kicks and spinning techniques. When Lopez began competing, kicks were scored by four corner judges and had to be forceful enough to elicit "trembling shock" from the opponent.
After controversy plagued the Beijing 2008 games, taekwondo's ruling body switched to an electronic system where players score when the sensors in their foot protectors strike their opponents' body armor with the right amount of impact; head kicks require only that the foot touch the opponent's head guard or face to register three or four points.
In recent years, many fighters have adapted to the temperamental system by modifying taekwondo kicks to maximize their chances, using unorthodox techniques that are unrecognizable to traditional taekwondo practitioners — including Lopez.
"It seems strange that with the rules now, if you land a kick, however it looks, it can score points even though it is not at all taekwondo," Lopez said, adding that he is reluctant to use some of the altered kicks being tried by many other fighters.
World Taekwondo Federation president Chungwon Choue said officials are trying to strike a balance between preserving the martial art's origins and the continued evolution of the sport. He noted Lopez would soon become the first athlete to make five straight Olympic appearances and that while most competitors were in their 20s, it would be unwise to discount Lopez.
"Anything can happen in taekwondo," Choue said.
Before arriving in Rio, Lopez said he is as excited as he was for his very first games.
"There will be a time that no matter how much I want it, I won't be capable of doing it," Lopez said. "So for right now, I am just trying to enjoy every single part of this."
Lopez wasn't the only taekwondo star to sustain a surprising loss Friday.
Moldova's Aaron Cook was routed, 14-2, by Taipei's Wei-Ting Liu. In the days leading up to the fight, Cook had talked about the possibility of meeting long-time rival and former countryman, England's Muhammad, in the gold medal match.
"I'm devastated," Cook told the Associated Press. "To have the opportunity to be here is amazing ... but I just feel like I've let everyone down today."
He later added: "It didn't go right for me on the biggest stage, and it's heartbreaking."
In the night session, Oh Hye-ri won the women's 67-kilogram division, giving South Korea its second gold medal of the Games.
Oh beat top-seeded Haby Niare of France in the final. Although Oh didn't score until the second round, she quickly landed numerous head shots within about 30 seconds to win 13-12.
The 28-year-old Oh also dominated her quarterfinal match against Chuang Chia-Chia of Taiwan, a fight that was stopped after Oh racked up an insurmountable 21-9 lead.
Oh previously competed in a heavier weight division, winning a world championship title.
The other South Korean to win Olympic gold in taekwondo at the Rio Games was Kim So-hui, who earned the title in the women's light flyweight division on Wednesday. The country, which won only one gold medal at the 2012 London Games, has also earned two bronze medals in taekwondo.
Ruth Gbagbi of the Ivory Coast and Nur Tatar of Turkey won the bronze medals on Friday.
In the men's event, Cheick Sallah Sisse won the 80-kilogram division by beating Lutalo Muhammad of Britain in the final, giving the Ivory Coast its first Olympic gold medal.
The third-seeded Sisse took the lead in the last second, landing a spinning kick just as the match ended to win 8-6.
Sisse ran to the stands, jumped a barrier and waved to the cheering crowd.
The bronze medals went Oussama Oueslat of Tunisia and Milad Beigi Harchgani of Azerbaijan.