PARIS -- It was another hot day at Roland Garros as China's Zheng Qinwen gave China a shot at a medal after getting through her second three-hour match in two days, while Rafael Nadal perhaps waved goodbye to his second home.

China's medal hopeful fought hard to qualify for the semifinals against German veteran Angelique Kerber. In a marathon 6-7 (4), 6-4, 7-6 (6) victory on Court Philippe-Chatrier, Zheng, still recovering from an equally tough match the day before, struggled to find her rhythm, committing 49 unforced errors and being broken five times.

For Kerber, this match marked the end of a successful career in which the German won three Grand Slams and an Olympic silver medal.

The first set was a rollercoaster as both players frequently broke each other's serve, neither able to dominate. The match began poorly for China's No. 1 when Zheng was broken in the first game, committing numerous unforced errors and allowing Kerber to gain an early advantage.

It took time for Zheng to find her flow against Kerber, who had announced her retirement before the tournament. Zheng broke back in the sixth game, shifting the momentum in her favor briefly. However, Kerber dug deep to break Zheng again while serving for the set, then held her own serve convincingly.

With the momentum on her side, Kerber broke Zheng for the third time in the set. When serving for the set, Zheng fought back, breaking Kerber for the third time to force a tiebreak. In the tiebreak, momentum continued to shift, but Kerber exploited Zheng's weakness on her second serve to win 7-4.

The second set saw both players initially hold their serves until Zheng broke after a lengthy deuce battle. But Zheng couldn't capitalize, immediately getting broken back by Kerber. Both players then held their serves for four games until Zheng broke Kerber again in the ninth game. Serving for the set, Zheng held firm and secured the set.

With rain expected, the roof was closed for the decisive third set, focusing the crowd's attention. Zheng struggled to maintain her momentum, getting broken without scoring in the third game.

In the following game, Zheng fought hard to break back, but Kerber held her serve after a tough battle over eight break points. As the match neared its conclusion, Zheng broke Kerber again. Despite the pressure on their serves, both players held, taking the third set to a tiebreak.

The battle of attrition reached its climax just shy of the three-hour mark. Despite Kerber taking the first point, Zheng pulled ahead, but Kerber closed the 6-3 gap to 6-6 on Zheng's serve.

With the crowd behind the veteran, the pressure was on Zheng to dig deep. An intelligent drop shot put Zheng back on match point, and a missed return by Kerber on Zheng's serve finally gave the Chinese sixth seed the victory after more than three hours of grueling tennis.

"Today's match was entirely about mental strength because I knew my performance wasn't as good as usual. I was under a lot of pressure, knowing what this match meant for me and for China. I am really happy for myself for winning this match, and I'm also happy for my team," Zheng admitted after the match. "Fighting for two or three hours for two consecutive days really tested my physical endurance."

"I think there are a lot of emotions. You know I gave everything I could on court. And I think this is what counts for me," Kerber said following her retirement. "Personally, I think the biggest success which I made, withstood a three-hour battle, match points saved, crazy battle for every point. And one of the biggest stages is that a summary of your career to go out."

Zheng will face Iga Swiatek in the semifinals. World No. 1 Swiatek and four-time French Open winner advanced to the Olympic semifinals after Danielle Collins retired with an injury in the final set. Swiatek dominated the first set 6-1, but Collins leveled by winning the second set 6-2 before her injury.

In men's singles action, No. 1 seed Novak Djokovic of Serbia overcame a spirited defense from Germany's Dominik Koepfer to emerge victorious 7-5, 6-3.

The writing seemed to be on the wall for Koepfer when Djokovic broke his serve to take a 3-1 lead in the first set, but the German clearly hadn't read the script when he immediately broke back to level proceedings at 3-3.

However, as the match wore on in the searing heat at Roland Garros, Koepfer seemed unable to maintain Djokovic's level of performance and consistency, and four unforced errors in the decisive 12th game condemned him to a first-set defeat.

Thereafter, it was rather more straightforward for Djokovic, who broke Koepfer in Game 4 of the second set, and maintained his composure to win all his remaining service games, closing out the match in one hour, 37 minutes.

Elsewhere in the men's singles, No. 2 seed Carlos Alcaraz of Spain also saw off his opponent inside two sets, beating neutral athlete Roman Safiullin 6-4, 6-2 in one hour, 30 minutes.

Safiullin initially had no answer to Alcaraz's powerful ground strokes as the Spaniard broke his serve twice to race into a 3-0 lead. However, the Russian soon grew into the contest, and broke Alcaraz to love in the next game before holding serve to make the score 3-2.

The No. 2 seed would not be denied thereafter, however, holding serve for the remainder of the set to close things out inside 45 minutes. Alcaraz then started the second set as he meant to go on, breaking Safiullin's serve to love in the very first game.

Though Safiullin hit back with some convincing baseline strokes of his own, Alcaraz would not be denied, winning all his service games and breaking Safiullin in especially impressive fashion at 5-2, notching a couple of clinical backhand winners.

However, in the doubles, Alcaraz crashed out of the men's doubles with the King of Clay Rafael Nadal, spelling what could be Nadal's final appearance at the venue in which he won a record 14 French Open titles.

The pair lost to specialist American doubles pair of Austin Krajicek and Rajeev Ram 6-2, 6-4. The American duo, seeded fourth, dominated the match and advanced to the semifinals.

The loss ends Spain's hopes for a men's doubles medal, now relying on Alcaraz in singles and Sorribes/Bucsa in women's doubles. Despite their individual talents, Nadal and Alcaraz struggled with their lack of doubles experience and Alcaraz's physical fatigue from previous singles matches.

In the closest match of the day, China's mixed doubles team of Zhang Zhizhen and Wang Xinyu went to three tie-breaks as they defeated the Australian pair of Ellen Perez and Matthew Ebden 6-7 (8), 7-6 (8), 10-5. There was nothing to separate the Chinese and Australians, who fought hard over every single point in their more than two-hour match.

Felix Auger-Aliassime defeated fourth seed Daniil Medvedev 6-3, 7-6 (5) to reach the Olympic quarterfinals for the first time. The Canadian showcased sharp serving and effective net play to counter Medvedev's baseline tactics. Despite the straight-set win, the match was closely contested, with Auger-Aliassime clinching the crucial points in a tight tiebreak.