Japan’s Kei Nishikori during his semifinal match against Luxembourg’s Gilles Muller at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, on Saturday, October 29, 2016. EPA/GEORGIOS KEFALAS

Croatia’s Marin Cilic returns to Germany’s Mischa Zverev during their semi final match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 29 October 2016. EPA/GEORGIOS KEFALAS

Germany’s Mischa Zverev reacts during his semifinal match against Croatia’s Marin Cilic at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 29 October 2016. EPA/GEORGIOS KEFALAS

Ivo Karlovic of Croatia serves a ball to Karen Khachanov of Russia during their quarter final match of the Erste Bank Open ATP tennis tournament in Vienna, Austria, 28 October 2016. EPA/LISI NIESNER

David Ferrer of Spain reacts after winning against Viktor Troicki of Serbia during their quarter final match of the Erste Bank Open ATP tennis tournament in Vienna, Austria, 28 October 2016. EPA/LISI NIESNER

Jo-Wilfried Tsonga of France serves the ball to Ivo Karlovic of Croatia during their semi final match of the Erste Bank Open ATP tennis tournament in Vienna, Austria, 29 October 2016. EPA/LISI NIESNER