Switzerland’s Roger Federer in action against USA’s Jack Sock during their semi final match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 31 October 2015. EPA/DOMINIC STEINMANN

Switzerland’s Roger Federer in action against Belgium?s David Goffin during their quarter final match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 30 October 2015. EPA/ALEXANDRA WEY

Switzerland’s Roger Federer in action against Spain’s Rafael Nadal during their final match at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 01 November 2015. EPA/GEORGIOS KEFALAS

Switzerland’s Roger Federer (L) celebrates after winning his final match against Spain’s Rafael Nadal (R) at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, 01 November 2015. EPA/GEORGIOS KEFALAS

Switzerland’s Roger Federer offers pizza to ball-boys after he won the final match against Spain’s Rafael Nadal at the Swiss Indoors tennis tournament at the St. Jakobshalle in Basel, Switzerland, on Sunday, November 1, 2015. EPA/KURT SCHORRER