Attila Balazs of Hungary returns the shot to Laslo Djere of Serbia during the semi-finals at 2019 ATP Croatia Open in Umag, Croatia, on July 20, 2019. Balazs won 2-0. (Xinhua/Igor Kralj)

Laslo Djere of Serbia serves during the semi-finals against Attila Balazs of Hungary at 2019 ATP Croatia Open in Umag, Croatia, on July 20, 2019. (Xinhua/Igor Kralj)

Salvatore Caruso of Italy returns the shot to Dusan Lajovic of Serbia during the semi-finals at 2019 ATP Croatia Open in Umag, Croatia, on July 20, 2019. Caruso handed over the match due to injury. (Xinhua/Igor Kralj)

Salvatore Caruso of Italy returns the shot to Dusan Lajovic of Serbia during the semi-finals at 2019 ATP Croatia Open in Umag, Croatia, on July 20, 2019. Caruso handed over the match due to injury. (Xinhua/Igor Kralj)

Dusan Lajovic of Serbia serves during the semi-finals against Salvatore Caruso of Italy at 2019 ATP Croatia Open in Umag, Croatia, on July 20, 2019. Caruso handed over the match due to injury. (Xinhua/Igor Kralj)