Juan Martin Del Potro outslugged John Isner 6-7(5) 6-3 7-6(4) 6-2 to reach the semi-finals of the U.S. Open on Tuesday after a towering battle in a sweltering Arthur Ashe Stadium.
The three hour, 31 minute quarter-final was played in suffocating humidity so extreme that officials called a halt to junior matches on the outside courts for more than two hours.
Anyone looking for serve and volley came to the wrong place as the pair traded bombs from the baseline with Isner, bidding to become the first American since Andy Roddick in 2006 to reach U.S. Open semi-finals, belting 26 aces and Del Potro 14.
Break chances were few and far between, Isner managed just three and was unable to convert any, while Del Potro had 11, cashing in on three, including one to close out the match.
It was enough to see Del Potro, the 2009 U.S. Open champion, through to the last four at Flushing Meadows for a third time where he will face top seed Rafa Nadal.