Del Potro keeps Rio dream alive

Rio de Janeiro - Juan Martin del Potro followed up his shock Olympics defeat of Novak Djokovic by downing Portugal's Joao Sousa on Monday in front of a legion of passionate, vocal Argentine fans.

The giant 27-year-old, ranked at 141 in the world after years of wrist injury misery had pushed him to the brink of quitting, swept to a 6-3, 1-6, 6-3 win over Sousa.

He goes on to face Japan's Taro Daniel where he will start favourite, especially if he again secures the support of the fans who turned centre court into a little corner of Buenos Aires on Monday.

Dressed in sky blue football shirts, they draped national flags and banners over the barriers and responded wildly when locals booed the mention of del Potro's name.

Meanwhile, the Olympic Games casualty count kept creeping upwards.

German 13th seed Philipp Kohlschreiber was forced to pull out with a broken foot, handing Slovakia's Andrej Marti a walkover into the third round.

Romania's Monica Niculescu gave a walkover to Russia's Svetlana Kuznetsova due to a lower back injury.

The women's draw had also to find four last-minute replacements for the first round.

Hsieh Su-wei of Taiwan withdrew from Rio after a row with her federation and was replaced by Lucie Hradecka of the Czech Republic.

Romania's Andreea Mitu was slotted in when Jelena Jankovic pulled out with a shoulder injury.

Ukraine's Lesia Tsurenko was replaced by Aleksandra Krunic of Serbia, while Galina Voskoboeva gave way to Kazakh compatriot Yaroslava Shvedova.

In the men's event, Dustin Brown of Germany and Andrey Kuznetsova of Russia were injured and retired from their first round matches on Sunday.

On Monday, it was the turn of Lucie Safarova of the Czech Republic to quit early when she retired from her match with Kirsten Flipkens of Belgium after dropping the first set.

Early action Monday saw German second seed and Australian Open champion Angelique Kerber recover from a 4-1 first set deficit to defeat Canada's Eugenie Bouchard, 6-4, 6-2.

It was Kerber's first win over the 2014 Wimbledon runner-up in three years.

"I am having one of the best years of my career," said Kerber.

"I won the Australian Open and I made the final at Wimbledon so I have a lot of confidence."

Bouchard, a former world number five but now at 40 in the rankings, believes she is closing in on a return to the top of the sport.

"I don't feel there's a big difference between the top players and the rest of the pack, it's one or two percent," said the 22-year-old.

There was also an early win for two-time Wimbledon champion Petra Kvitova who put out Caroline Wozniacki 6-2, 6-4.

US seventh seed Madison Keys came out on top in a three-hour duel against Kristina Mladenovic of France 7-5, 6-7 (4/7), 7-6 (7/5).

Martina Hingis, playing in her first Olympics in 20 years, teamed up with Timea Bacsinszky to reach the women's doubles second round.

The Swiss pair defeated Coco Vandeweghe and Bethanie Mattek-Sands of the United States 6-4, 6-4.

Later Monday, defending women's champion Serena Williams, chasing a fifth gold medal, takes on Alize Cornet of France.

Cornet defeated the American star three times in 2014 including at Wimbledon.

Japan's Kei Nishikori meets Australia's John Millman who created history in the first round when he recorded the first 'double bagel' 6-0, 6-0 win in Olympic history.

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