Switzerland’s Roger Federer returns to Luxembourg’s Gilles Muller during their first round match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 22 October 2014. EPA/GEORGIOS KEFALAS

Bulgaria’s Grigor Dimitrov returns a ball to Germany’s Alexander Zverev during their first round match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 22 October 2014. EPA/GEORGIOS KEFALAS

Spain’s Rafael Nadal returns a ball to France’s Pierre-Hugues Herbert during their round of sixteen match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, on Wednesday, October 22, 2014. EPA/GEORGIOS KEFALAS

Switzerland’s Roger Federer serves to Luxembourg’s Gilles Muller during their first round match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 22 October 2014. EPA/GEORGIOS KEFALAS

Bulgaria’s Grigor Dimitrov returns a ball to Germany’s Alexander Zverev during their first round match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 22 October 2014. EPA/GEORGIOS KEFALAS

Spain’s Rafael Nadal returns to France’s Pierre-Hugues Herbert during their round of sixteen match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 22 October 2014. EPA/GEORGIOS KEFALAS