Donald Young of the US reacts as he plays Viktor Troicki of Serbia during their match on the sixth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center in Flushing Meadows, New York, USA, 05 September 2015. The US Open runs through 13 September, which is a return to a 14-day schedule. EPA/JOHN G. MABANGLO

Donald Young of the US hits a return to Viktor Troicki of Serbia during their match on the sixth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center in Flushing Meadows, New York, USA, 05 September 2015. The US Open runs through 13 September, which is a return to a 14-day schedule. EPA/JOHN G. MABANGLO

Donald Young of the US reacts after defeating Viktor Troicki of Serbia during their match on the sixth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center in Flushing Meadows, New York, USA, 05 September 2015. The US Open runs through 13 September, which is a return to a 14-day schedule. EPA/JOHN G. MABANGLO

Donald Young of the US reacts after defeating Viktor Troicki of Serbia during their match on the sixth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center in Flushing Meadows, New York, USA, 05 September 2015. The US Open runs through 13 September, which is a return to a 14-day schedule. EPA/JOHN G. MABANGLO

Donald Young of the US reacts after defeating Viktor Troicki of Serbia during their match on the sixth day of the 2015 US Open Tennis Championship at the USTA National Tennis Center in Flushing Meadows, New York, USA, 05 September 2015. The US Open runs through 13 September, which is a return to a 14-day schedule. EPA/JOHN G. MABANGLO