Jannik Sinner of Italy returns the shot to Perdro Sousa of Portugal during the first round match at 2019 ATP Croatia Open in Umag, Croatia, on July 15, 2019. Jannik Sinner won the match 2-1. (Xinhua/Goran Stanzl)

　　Perdro Sousa of Portugal serves during the first round match against Jannik Sinner of Italy at 2019 ATP Croatia Open in Umag, Croatia, on July 15, 2019. Perdro Sousa lost 1-2. (Xinhua/Goran Stanzl)

　　Jiri Vesely of the Czech Republic returns the shot to Cedrik-Marcel Stebe of Germany during the first round match at 2019 ATP Croatia Open in Umag, Croatia, on July 15, 2019. Jiri Vesely won the match 2-1. (Xinhua/Goran Stanzl)

　　Slovenia's Aljaz Bedene reacts during the first round match against Italy's Marco Cecchinato at 2019 ATP Croatia Open in Umag, Croatia, on July 15, 2019. Bedene won 2-0. (Xinhua/Goran Stanzl)