Crowd gathers to watch Nadal warm up before U.S. Open semi-final

FILE PHOTO - Sep 6, 2017; New York, NY, USA; Rafael Nadal of Spain waves to the crowd after his match against Andrey Rublev of Russia (not pictured) on day ten of the U.S. Open tennis tournament at USTA Billie Jean King National Tennis Center. Mandatory Credit: Geoff Burke-USA TODAY Sports

NEW YORK (Reuters) - A crowd gathered to watch world number one Rafael Nadal warm up in Arthur Ashe Stadium on a cool and windy Friday at the U.S. Open, ahead of his semi-final showdown with Argentine Juan Martin del Potro later in the day.

Nadal has faced little adversity at the tournament so far, dropping just two sets in his five matches and blowing out 19-year-old Russian Andrey Rublev in straight sets to reach the semi.