Guido Pella of Argentina competes against Robin Haase of the Netherlands during the men's singles semifinal match at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Guido Pella won 2-1. (Xinhua/Igor Soban)

Guido Pella of Argentina competes against Robin Haase of the Netherlands during the men's singles semifinal match at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Guido Pella won 2-1. (Xinhua/Igor Soban)

Robin Haase of the Netherlands competes against Guido Pella of Argentina during the men's singles semifinal match at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Robin Haase lost 1-2. (Xinhua/Marko Prpic)

Guido Pella of Argentina competes against Robin Haase of the Netherlands during the men's singles semifinal match at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Guido Pella won 2-1. (Xinhua/Igor Soban)

Matwe Middelkoop (L) and Robin Haase of the Netherlands react during the men's doubles final match against Roman Jebavy and Jiri Vesely of the Czech Republic at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Robin Haase and Matwe Middelkoop won 2-0. (Xinhua/Marko Prpic)

Jiri Vesely (R) and Roman Jebavy of the Czech Republic react during the men's doubles final match against Robin Haase and Matwe Middelkoop of the Netherlands at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Jiri Vesely and Roman Jebavy lost 0-2. (Xinhua/Marko Prpic)

Jiri Vesely (L) and Roman Jebavy of the Czech Republic compete during the men's doubles final match against Robin Haase and Matwe Middelkoop of the Netherlands at 2018 ATP Croatia Open in Umag, Croatia, July 21, 2018. Jiri Vesely and Roman Jebavy lost 0-2. (Xinhua/Marko Prpic)