Taro Daniel bowed out in the opening round of the Rakuten Japan Open on Tuesday, losing 6-1, 6-3 to No. 5 seed Stefanos Tsitsipas of Greece.
A wildcard entry to the tournament, the 72nd-ranked Daniel struggled to hold serve against the aggressive baseline play of world No. 15 Tsitsipas at Musashino Forest Sport Plaza.
In the opening set, the 20-year-old Tsitsipas won seven of 14 points on the 25-year-old Daniel's first serve and three of eight against his second serve.
Daniel, who last month helped Japan win its Davis Cup World Group tie against Bosnia-Herzegovina, was unable to break Tsitsipas throughout the match, earning just one break point against the youngest player in the ATP top 20.
Tsitsipas won 25 of 29 points on his own first serve, sending down five aces on his way to winning the first meeting between the pair in 1 hour, 15 minutes.
Tsitsipas will face the winner of Wednesday's opening-round match between Gilles Simon of France and Australia's Alex De Minaur.
In other first-round action, Germany's Jan-Lennard Struff pulled off a major upset, beating top-seeded Croatian Marin Cilic 3-6, 6-4, 7-6 (7-1).
World No. 56 Struff sent down nine aces to Cilic's 12 and converted three of 12 break points, improving to 1-1 for his career against the world No. 6.
Struff will face Frenchman Jeremy Chardy in the last 16. Chardy advanced with a 4-6, 6-3, 6-3 win over Damir Dzumhur of Bosnia-Herzegovina.
