Simone Biles will not defend her Olympic title in Thursday's individual all-around competition in order to focus on her mental health, USA Gymnastics has confirmed.
The four-time gold medallist from Rio completed only one event in Tuesday's team competition at the Ariake Gymnastics Centre, registering the lowest score of the first rotation.
Biles left the floor with a trainer and, although she later returned donned in a tracksuit, she opted not to continue and remained to support her team-mates who could only secure silver behind the Russian Olympic Committee.
Following the team event, Biles opened up on her struggles at Tokyo 2020 and said she would take it day-by-day before making a decision.
USA Gymnastics subsequently announced she will not participate on Thursday and will continue to be evaluated before a decision is made on whether she takes part in the individual event finals, which take place next week.
"After further medical evaluation, Simone Biles has withdrawn from the final individual all-around competition at the Tokyo Olympic Games, in order to focus on her mental health," a USA Gymnastics statement read.
"Simone will continue to be evaluated daily to determine whether or not to participate in next week’s individual event finals. Jade Carey, who had the ninth highest score in qualifications, will participate in her place in the all-around."
USA Gymnastics hailed Biles for her decision to put her own well-being ahead of competing.
"We wholeheartedly support Simone's decision and applaud her bravery in prioritising her well-being," the governing body added.
"Her courage shows, yet again, why she is a role model for so many."
Los Angeles Dodgers' star Cody Bellinger produced an unbelievable error gifting the San Francisco Giants a decisive run in their 2-1 victory in the MLB on Tuesday.
With scores locked at 1-1 after the sides traded runs in the fifth and sixth innings, Bellinger inexplicably threw several feet over third baseman Justin Turner, allowing Buster Posey in for the go-ahead run.
Bellinger is normally at center field but was moved to first base to ease the stress on his sore hamstring, but that came back to bite the Dodgers.
At the bottom of the eighth, Dodgers reliever Blake Treinen had walked Posey and Mike Yastrzemski, before Darin Ruf grounded to second baseman Max Muncy who threw to Bellinger for an out.
But then the first baseman opted to send the ball to third to try out Posey, only to deliver a costly wayward throw.
"I don’t know how I would have thrown it that high. It was a horrible throw," Bellinger said. "I’ll go back and watch it on video and see what happened on that play.”
Home runs for Ohtani and Tatis
Shohei Ohtani's Los Angeles Angels may have lost 12-3 to the Colorado Rockies at home but he provided a highlight with a two-run home run in the fifth inning with his side 10-0 down.
The homer registered 110.4 mph exit velocity and a projected distance of 463 feet. It was also Ohtani's league-high 36th home run this season.
Fernando Tatis Jr also homered, bringing up his 31st of the season, with a two-run shot in the San Diego Padres' 7-4 victory over the Oakland Athletics. The Padres were trailing 3-0 at the time.
Eloy Jimenez creamed a decisive three-run homer which travelled 459 feet to lift the Chicago White Sox to a 5-3 triumph over the Kansas City Royals.
Bryce Harper hit a rare inside-the-park home run as the Philadelphia Phillies lost 6-4 to the Washington Nationals.
Joey Votto was feeling it as he hit two home runs as the Cincinnati Reds won 7-4 over the Chicago Cubs.
Diamondbacks downed by struggling Rangers
The Texas Rangers ended their 10-game losing streak with a 5-4 victory over the Arizona Diamondbacks, who continue to struggle. The Diamondbacks allowed all five runs in the fourth inning and slump to a 31-71 record, having only won 12 games on the road from 53, which is the best worst away record in the majors.
Riley's six-RBI game
Austin Riley hit a grand slam and a two-run home run as the Atlanta Braves won 12-5 over the New York Mets. The third baseman moved up to 19 homers for the season, recording his second-ever career grand slam, totalling six RBI for the game.
Tuesday's results
Washington Nationals 6-4 Philadelphia Phillies
Milwaukee Brewers 9-0 Pittsburgh Pirates
Miami Marlins 7-3 Baltimore Orioles
Atlanta Braves 12-5 New York Mets
New York Yankees 4-3 Tampa Bay Rays
St Louis Cardinals 4-2 Cleveland Indians
Texas Rangers 5-4 Arizona Diamondbacks
Cincinnati Reds 7-4 Chicago Cubs
Chicago White Sox 5-3 Kansas City Royals
Detroit Tigers 6-5 Minnesota Twins
Colorado Rockies 12-3 Los Angeles Angels
San Francisco Giants 2-1 Los Angeles Dodgers
San Diego Padres 7-4 Oakland Athletics
Houston Astros 8-6 Seattle Mariners
Dodgers at Giants
Two of the best meet on Wednesday when the San Francisco Giants (63-37), leaders in the National League, host reigning world champions, the Los Angeles Dodgers (61-41).
Katie Ledecky called on a source of inspiration close to home as she ended her wait for a gold at the Tokyo Games with victory in the women's 1500m freestyle final.
Ledecky, who Olympic great Micheal Phelps hailed as "the best female swimmer that we have ever seen", had endured a frustrating start to the Games, failing to defend the 200 metre and 400m free golds which she won at Rio 2016.
Australia's Ariarne Titmus has instead enjoyed the breakthrough to stardom this time around, but Ledecky finally struck gold in Tokyo as she powered to glory in the maiden women's 1500m event.
It took her total of Olympic golds to six – the 24-year-old becoming the fourth female swimmer to reach that mark, after compatriots Jenny Thompson (eight) and Amy van Dyken (six), and Germany's Kristin Otto (six).
Ledecky, who clocked in at 15:37.34, is also just the fourth American woman to claim six golds, after Thompson, Van Dyken and Allyson Felix.
Erica Sullivan clinched silver to seal a one-two for Team USA, and Ledekcy revealed her thought process following a disappointing fifth-place finish in the 200m race.
"After the 200, I knew I had to turn the page very quickly and in the warm-down pool I was just thinking of my family," said Ledecky, who has now won gold medals at three different Games, following success in London, at the age of 15, and Rio.
"Each stroke I was thinking of my grandparents. They're the toughest four people I know and that's what helped me get through that.
“It means a lot. People maybe feel bad that I'm not winning everything, but I want people to be more concerned about other things in the world. People are truly suffering. I'm just proud to bring home a gold medal to Team USA.”
Sullivan's silver handed the USA's first one-two finish in a women's swimming race since Sydney 2000, when Brooke Bennett and Diana Munz wrapped up the top prizes in the 400m freestyle.
“I'm so happy to go one-two with Erica," Ledecky added. "It is the first women's 1500m (freestyle in Olympic history) so I couldn’t have a better outcome than that. I’m so, so happy."
Sarah Kohler completed the podium to become the first German swimmer to win an Olympic medal since 2008.
One of the enduring images of Tokyo 2020 will be the sight of Dean Boxall's exuberant celebrations after Ariane Titmus won an epic women's 400 metres freestyle race.
It was the sheer joy and exuberance on the face of the rock-star looking coach as he wildly revelled in the momentous achievement of his pupil, who had just toppled the great Katie Ledecky in the most sensational fashion.
"I can't help it. I bleed with my athletes. When they leave the pool deck with me – whether I'm having a chat with them for an hour if it has to be – but when they leave, they have to start the recovery process and go home. They switch off. I don't. I go home and dream for them. I go home and try and find a way for them to get better," Boxall explained after he had gone viral on social media.
Titmus herself saw the funny side.
"That's just the way Dean is," she said. "He's very passionate about what he does – he really becomes quite animated.
"This is just as much for him as it is for me. He has sacrificed a lot in his family life, his kids and his wife, for his job. He puts 100 per cent into being a swimming coach. I would not be here without him."
But it was something else Boxall said that really went furthest to explaining his emotional display.
"I've been with her for five years. Having a dream together. Katie was so far in front of us that in the beginning when I started to coach her I couldn't even have this conversation," he said.
"When Arnie came to me she was a 4.12 [in the 400m]. At that stage Katie went 3.56. That's 16 seconds. We just started chipping away, we started to believe."
From a dream, to belief, to the reality of being an Olympic champion.
On Wednesday, Titmus would confirm her status as a breakout star of Tokyo 2020 with another victory in the 200m free filled with fight, desire and a never-say-die attitude.
Billed as Titmus versus Ledecky II, there was a sense of deja vu about Litmus' performance but another battle with her equally brilliant rival – now a six-time gold medallist over three Games after winning the first ever Olympics women's 1500m race – failed to transpire as the American could only finish fifth.
Instead it was Hong Kong's Siobhan Haughey who brought the very best out of Titmus. It took a huge effort down the final 50m to break the Olympics record in a time of 1:53.50.
At the medal ceremony there were tears and a warm embrace with Boxall, the emotion spilling out of this cool customer after becoming just the third Australian, along with Shane Gould and Ian Thorpe, to complete a 200 and 400m free double at a single Olympics.
"I feel like I'm pretty good at containing my emotion I knew that's something I had to do after the 400 because the 200 was right after," Titmus told a news conference after doubling up.
"Now that I haven't got a swim tonight I think I kind of let it out a bit, seeing him [Boxall] and seeing him emotional makes me emotional because this is a great partnership, this isn't just me winning, this is him winning so I think that's why I got so emotional."
For the uninitiated, this week is not the first time Titmus has triumphed over Ledecky, the 20-year-old from Tasmania having taken out the gold at the 2019 World Championships in Gwangju.
But Ledecky, who had won the 200 and 400m free at Rio in 2016, had been contending at that meet with a stomach virus and prior to this week it was far from certain where the golds were headed.
Titmus has emphatically answered the question, though, and it is her personable qualities that have made her resonate this week.
So too have the ferocity, tenacity and sheer awesome speed of her performances.
The Aquatics Centre, as Titmus herself adhered to when addressing the media, provides about as close to a normal experience as you're likely to find at Tokyo 2020. While there are still swathes of empty seats in this 15,000 capacity venue, there are areas designated to team-mates and coaches – all cheering, chanting and applauding to create at least some semblance of an Olympics atmosphere.
But it is Litmus' displays that have brought true electricity, not only to the pool but for the Games at large.
Two more chances at gold lie in wait in the 800m (where Ledecky, a gifted long-distance swimmer, is favourite) and the 4x200m freestyle relay.
Regardless of what happens in those races, a new star has been born.
Sixth seed John Isner sent down an Atlanta Open joint record 36 aces as he overcame countryman Jeffrey John Wolf in three sets on Tuesday.
World number 35 Isner was dominant on his first serve, winning 6-4 6-7 (3-7) 6-4 to claim a spot in the second round where he will face Jack Sock who beat Ricardas Berankis in three.
Isner's 36 aces equaled the previous Atlanta Open record set by Sam Querrey on Monday in his three-set win over Peter Gojowczyk.
American fifth seed Taylor Fritz also progressed on Tuesday with a 6-3 6-4 victory over Russian Evgeny Donskoy.
French seventh seed Benoit Paire got past Japan's Yasutaka Uchiyama 7-5 6-7 (2-7) 6-4, while enigmatic Australian Nick Kyrgios beat South African Kevin Anderson 7-6 (7-4) 6-3.
Teenage American talent Brandon Nakashima knocked out Trent Bryde, while Australian Chris O'Connell beat Denis Kudla and Finland's Emil Ruusuvuori got past Mackenzie McDonald 7-6 (7-3) 7-5.
Nakashima, who got a special exemption entry into the Atlanta Open, next takes on top seed Milos Raonic.
Ariarne Titmus stole the show again in the pool at Tokyo 2020, while Yui Ohashi also doubled up and Katie Ledecky got herself on the gold trail.
Australia's Titmus was back competing against Ledecky just two days on from their epic in the 400m free, though the latter was not in medal contention this time in the shorter 200.
However, the American – who has previously described herself as a "distance swimmer with a sprinter's mentality" – did become a six-time Olympic gold medallist on Wednesday.
Here's a round-up from the Tokyo Aquatics Centre.
TERRIFIC TITMUS DOUBLES UP
Wednesday's 200m freestyle race was billed as Titmus versus Ledecky II, with the former upstaging her American rival in the 400m free in a thriller two days earlier.
This time Ledecky was off the pace down in fifth and it was Hong Kong's Siobhan Haughey providing the test as Titmus had to pull one out of the bag again to get the gold.
A storming last 50m propelled her to a new Olympic record time of 1:53.50 and cemented her status as a breakout star.
"I could see I was trying to mow Siobhan down on the third 50. I had no idea where she was on the last lap. I knew I had Penny [Oleksiak, bronze] covered but Siobhan was the person that was there," Titmus said.
"I felt a little bit that was there. I felt a little bit - my legs started to go a bit but I'm happy to get it done."
Titmus joins Shane Gould and Ian Thorpe as the only Australians to complete a 200/400m freestyle double at a single Games.
JOY OF SIX FOR LEDECKY
She may have been unable to retain two of her titles from 2016 but the awesome Ledecky added to her gold medal haul with a dominant win in the first ever women's 1500m free Olympics final.
The American came home in 15:37.34 to lead a US one-two from Erica Sullivan.
Ledecky has now won gold medals at three different Games, having also topped the 800m free podium at London 2012.
OHASHI MARVELS IN IM ONCE MORE
Another star of these Games has been Ohashi, who will have delighted the Japanese fans watching at home after adding to her 400 individual medley crown in the shorter 200m race.
A race tipped to be wide open proved to be so with Ohashi battling stroke-for-stroke down the final 50m with American Alex Walsh, who was pipped by just 0.13 seconds.
Walsh's compatriot Kate Douglass rounded off the podium in third.
MILAK MAULS RIVALS
You can never be fully certain of an outcome in any sport but Kristof Milak was about as close to a shoo-in in the men's 200m butterfly as you can get.
So it proved to be. The Hungarian at least had the good decency to allow his rivals to believe they had a chance before absolutely blasting them out the water with his trademark finishing power.
Milak came home in a time of 1:51.25, a new Olympic benchmark and only half a second off his own world-record time. Japan's Tomoru Honda took silver from lane eight, some 2.48 seconds adrift.
DOUBLE DELIGHT FOR DEAN AS TEAMGB STAR IN RELAY
There was to be no record for TeamGB in the men's 4x200 free but they utterly dominated the competition to bring home gold in a time of 6:58.58.
Tom Dean, champion over the distance in the individual race on Tuesday, anchored the first leg before James Guy hit the front on his stint.
Matt Richards further stretched the advantage and Duncan Scott – who took silver behind Dean – brought it home in style with the Russian Olympic Committee over three seconds behind to take silver.
Australian swimming star Ariarne Titmus says her gold medal winning heroics are yet to fully sink in after de-throning Katie Ledecky to win the women's 200m freestyle on Wednesday.
Titmus edged out Ledecky in Monday's women's 100m freestyle final and backed that up with her second gold medal at the 2020 Tokyo Olympics.
The Australian won in 1:53:50, setting a new Olympic record, as she edged out Hong Kong's Siobhan Haughey by 0.42 seconds.
Canada's Penny Oleksiak claimed bronze, with five-time Olympic gold medallist Ledecky finishing down in fifth.
Titmus looked calm and composed in the pool after winning her second gold, with further races to come into the 4x200m freestyle relay and 800m freestyle.
"I don’t think it'll settle in until I get home and have a rest," Titmus told Australian TV network 7 after the race. "When you're in this situation you have to compartmentalise everything.
"I think once I stop racing, I think I'll release everything. On to the relay and 800m now. I don't want to ruin the rest of my meet by celebrating too hard. I'm proud with what I've achieved."
Haughey led Titmus at the final turn but the Australian stormed home over the last 50m, similar to Monday's win over Ledecky, although she said her "legs started to go".
"I was trying to mow Siobhan down in the third 50," Titmus said. "I had no idea where she was in the last five.
"I knew I had Penny covered but Siobhan was the person that was there. At the end my legs started to go but I'm happy to get it done."
She added: "Before we left, Sydney went into lockdown, it's really sad. I'm happy that the Olympics are here and we can hopefully bring some excitement to loungerooms.
"I'm fortunate to be here. I'm from a small town in Tassie [Tasmania]. It goes to show, if you believe you can do something, you can 100 per cent do it if you work for it."
Team USA star forward Kevin Durant remains bullish about the side's ability to adjust their game in their pursuit of a gold medal at the 2020 Tokyo Olympics.
USA were beaten 83-76 by France in their opening game at the Tokyo Olympics having been beaten by Australia and Nigeria in exhibition games in the lead-up.
The losses have led to criticism of the cohesion of Team USA who are 15-time Olympic gold medalists, but Durant insisted there was no panic ahead of Wednesday's second group game against Iran.
"Our adjustment is we just make more shots," Durant said. "We've got the best talent in the world on the team."
USA led throughout the first half against France before collapsing down the stretch, surrendering a 74-67 advantage.
"We got each other good shots," Durant added. "We know how to play off each other."
USA assistant coach Lloyd Pierce reiterated Durant's calmness about the situation, stating they need to remain confident.
"The keys to beating these guys is just being ourselves, worrying about what we do best," Pierce said.
"We want to get out and play fast and create extra possessions throughout the course of the games.
"It's only 40 minutes, we have to make this game a little bit faster and get as many easy shots as we can.
"We have to be ourselves as well. Our guys have to play with confidence, have to play with the freedom they're used to, they also have to do that together, make simple plays, quick plays and enjoy the experience."
Brooklyn Nets forward Durant provided a positive assessment of the impact of Khris Middleton, Jrue Holiday and Devin Booker who played against France after competing in the NBA Finals last week.
The trio arrived barely 48 hours before the France game, with Holiday top scoring with 18 points plus four assists from 27 minutes.
Booker shot poorly, with four points and three assists from 18 minutes, while Middleton only had five minutes of game time.
"What they did to me felt like just who they are," Durant said. "I always have a high-level respect for all three of those guys.
"For them to come out and play, not really complain about anything, be excited to be here [full credit]. Those guys are amazing talents, it's great being around them."
Washington Nationals short-stop Trea Turner has been pulled mid-game on Tuesday after testing positive to COVID-19.
Turner had already hit an infield single and scored on a home run in Tuesday's game against the Philadelphia Phillies.
The 28-year-old went down the tunnel after touching down on home plate and did not re-appear to take to the field at the bottom of the first inning.
The Nationals later confirmed that Turner's premature removal was due to testing positive to COVID-19.
Turner, who has hit .320/.368/.519 in 95 games this season with 124 hits and 18 home runs, has been linked with a move away from Washington ahead of Friday's MLB Trade Deadline.
Alex Ovechkin’s pursuit of the NHL’s all-time record for goals scored will continue with the only franchise he has ever played for after the Washington Capitals re-signed their captain to a five-year, $47.5 million contract on Tuesday.
Ovechkin, drafted first overall by the Capitals in 2004, is the franchise leader in games played (1,197), goals (730) and points (1,320) since making his NHL debut in 2005-06. He led the Capitals to their first Stanley Cup championship in 2018.
Ovechkin’s $124 million, 13-year contract was set to expire before NHL free agency officially begins on Wednesday.
''Alex is the face of our franchise and is committed to this organisation and this city,'' Capitals general manager Brian MacLellan said. '
"'Alex embodies what our franchise is all about, and we're thrilled that he will continue his career in the Caps uniform for the next five years.''
Ovechkin’s 730 career goals rank sixth all-time behind Wayne Gretzky (894), Gordie Howe (801), Jaromir Jagr (766), Brett Hull (741) and Marcel Dionne (731).
Now signed through the 2025-26 season, Ovechkin – who turns 36 in September – would have to average nearly 33 goals per season during the life of his new contract to surpass Gretzky
Host nation Japan remain top of the Olympic Games medal table, one gold medal clear of the United States and China, thanks to another two gold medals on Tuesday in Tokyo.
Japan now have 10 golds at the Games, five of which have come in Judo, despite home favourite Naomi Osaka crashing out to Czech world number 42 Marketa Vondrousova in the women's singles tennis.
The USA extended their gold medal count to nine, with 17-year-old Lydia Jacoby stealing the headlines courtesy of gold in the 100m breaststroke – their third in the pool so far – though they had to settle for silver in softball as they lost to table-toppers Japan.
China, who have dominated the shooting to win eight medals in nine events, picked up three more golds with success in the 10m air pistol mixed event, the 10m air rifle mixed event and the women's 10m synchronised platform - their second diving gold in Tokyo.
The Russian Olympic Committee remain fourth with seven golds after winning the day's big event, the women's team artistic gymnastics, but that was overshadowed due to American Simone Biles withdrawing due to concerns over her mental health.
The Russians surprised in the pool, too, with Evgeny Rylov claiming 100m backstroke gold that forced defending Olympic champion Ryan Murphy to settle for bronze – that result represented the USA's first backstroke defeat since the 1992 Barcelona games.
After team-mate Adam Peaty's call for a British gold surge, Tom Dean and Duncan Scott made history by winning the first British swimming one-two since 1908 in the 200m freestyle.
Dean and Scott's swimming achievements capped a positive day for Great Britain that saw them collect six medals in total to stay in fifth place.
Meanwhile, Flora Duffy made history for Bermuda with gold in the women's triathlon as the tiny Caribbean island became the smallest country to ever win Gold at the Summer Games.
There was plenty of drama in Tokyo on Tuesday and that is set to continue as the Olympic Games ramps up further on Wednesday.
A titanic tussle in the swimming pool should be well worth watching, but action on the bikes and in the basketball court will also draw plenty of eyes.
Stats Perform guides you through the events not to be missed.
TITMUS OUT TO TOP LEDECKY AGAIN
Katie Ledecky is one of the dominant forces in the pool, taking gold in each of her prior four individual Games finals since her 2012 debut as she headed to Tokyo, but she was upset in the 2020 opener.
Ariarne Titmus, the 20-year-old Australian, beat the United States' world record holder by more than half a second in the 400m freestyle final.
Now, Titmus is coming for Ledecky's crown again as the pair do battle in the 200m freestyle, where another victory would send a significant message.
TOUR STARS TAKE ON TIME TRIAL
There are no shortage of big names in the men's time trial, with a number of Grand Tour winners involved – including Geraint Thomas, no doubt determined to put on a show after his fall in the road race.
The last two men to head out perhaps represent the most likely Olympic champions, though, as Wout van Aert and Filippo Ganna go for gold.
Van Aert won the final two stages of the Tour de France, including a time trial on the penultimate day of the race.
FOCUS ON THE FOUR
The first rowing medals of the Games are to be handed out on Wednesday, and the women's four – back in the Olympics for the first time in 30 years – should provide plenty of intrigue.
World champions Australia changed their line-up for the Olympics, having not competed internationally since taking their title in 2019. Meanwhile, the Netherlands, world silver medallists and back-to-back European champions, have been dominant.
The two teams won their respective heats, but Australia's time of six minutes and 28.76 seconds was an Olympic best and almost five seconds quicker than the Dutch. Whether that chasm will remain when the boats are side by side is another matter.
TWO-WAY TUSSLE IN THE GYM
There is more gymnastics action to look forward, with the men's individual final taking place.
Home hope Daiki Hashimoto qualified with the best score and was outstanding for Japan in the team event, yet could only take silver as the hosts were pipped by the Russian Olympic Committee.
It was Nikita Nagornyy's floor routine which sealed that Russian success and he will be bidding for another gold, having trailed Hashimoto in second in qualification.
CAN DREAM TEAM RECOVER FROM NIGHTMARE START?
The United States' latest men's basketball title defence started in miserable fashion with a defeat to France, the team who eliminated them at the 2019 FIBA Basketball World Cup.
It was Team USA's first Olympics loss since 2004, but it is highly unlikely a second will follow as they face Iran. A big performance is needed regardless to calm the critics.
While France delivered the upset in the basketball, they face their own humiliation in the football. Only a two-goal win against hosts Japan, themselves needing a point, will secure progress through Group A for Les Bleus.
Simone Biles said she had put her "mental health first" after missing out on adding a fifth Olympic gold medal to her collection following an early withdrawal from the women’s team final.
The 24-year-old gymnastics icon revealed she was “dealing with things internally” after a disappointing performance on the vault.
Biles posted the lowest score of the first rotation on Tuesday as she landed awkwardly after failing to execute an Amanar, while only completing a Yurchenko 1.5 twist.
After she subsequently withdrew, Team USA had to settle for a silver medal behind the Russian Olympic Committee while Great Britain completed the podium.
Biles admitted that she was "fighting demons", explaining: "I just don't trust myself as much as I used to. I don't know if it's age. I'm a little bit more nervous when I do gymnastics. I feel like I'm also not having as much fun."
She added: "I say, 'put mental health first'. Because if you don't, you won't enjoy sport and won't succeed as much as you want to.
"So it's okay sometimes to sit out the big competitions to focus on yourself, because it shows how strong a competitor and person that you really are, rather than just battling through it."
OSAKA STUNNED
The big names continue to tumble in the women’s singles tennis event, with second seed Naomi Osaka defeated in straight sets.
The home favourite, who lit the Olympic cauldron on Friday, was denied a place in the quarter-finals after being ousted 6-1 6-4 by world number 42 Marketa Vondrousova.
This event marked Osaka’s first competitive tennis in two months since her early withdrawal from the French Open at the end of May, citing mental health issues.
The world number two is the latest of the big names to fall at the Tokyo Games, with top seed Ash Barty and third seed Aryna Sabalenka also suffering early exits.
"Of course, it's one of the biggest wins of my career," Vondrousova said. "Naomi is a great player, so I knew it would be a tough match.
“I'm very happy with my play. I played amazingly in the first set, and then the second set was really tough. I'm just happy to be through."
ARGENTINA RECOVER TO SEE OFF SPRINGBOKS
Argentina recovered from a dreadful start to beat South Africa and book their place in the rugby seven semi-finals.
Trailing 7-0 after just under two minutes, the Pumas were then reduced to six men when Gaston Revol - who was reduced to tears - was shown a straight red card.
Nevertheless, they demonstrated tremendous resilience and character before eventually running out 19-14 winners.
Argentina will play Fiji in the last four after the reigning Olympic champions swept Australia aside 19-0.
Great Britain stormed back from 21-0 down to beat the USA, scoring four tries to secure a dramatic 26-21 victory.
Team GB will play New Zealand, who eased to a 21-10 success over Canada.
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