Stefanos Tsitsipas and Alexander Zverev have made winning debuts at the Tokyo Olympics but Andrey Rublev is out after defeat from Kei Nishikori.
Zverev made a straightforward start to his Olympic campaign on Sunday with a 6-1, 6-3 victory over Chinese Taipei’s Yen-Hsun Lu.
The fourth seed was never under pressure through his match and admitted just before the tournament started that he see's himself as 'one of the favourites' to win it. He will now face Columbian Daniel Elahi Galan in the next round.
Stefanos Tisitipas had a less straightforward match against German Philipp Kohlschreiber, which went the full three sets, and the Greek had to come back from a break down in the third to win 6-3, 3-6, 6-3.
In winning the match, Tsitsipas, who is third seed, became the first Greek man to win an Olympic singles tennis match since 1924. He will now face American Frances Tiafoe in the next round.
Former Olympic bronze medalist Kei Nishikori overwhelmed fifth seed Andrey Rublev in their first round clash winning in straight sets 6-3, 6-4.
It is the fourth Olympics for Nishikori as opposed to Rublev's first and experience showed on court, with the Russian converting only one of five break points he had on Nishikori's serve. The Japanese star will now face American Marcos Giron in the second round.
Seventh seed Hubert Hurkacz also advanced as he defeated Australian Luke Saville 6-2, 6-4. Karen Khachanov rallied back to beat Japan’s Yoshihito Nishioka 3-6, 6-1, 6-2, while Argentinian Diego Schwartzman overcame Peruvian Juan Pablo Varillas 7-5, 6-4.
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