Can't believe I will play in semis, says del Potro

Juan Martin Del Potro of Argentina, who defeated 19-time Grand Slam champion Roger Federer in the US Open quarterfinals, said that he played the best match of the tournament.

Del Potro came out with a vintage display of power tennis and defeated Federer 7-5, 3-6, 7-6, 6-4, to advance to the semifinals at the Flushing Meadows for the first time since winning the title in 2009, when he defeated the Swiss maestro in a classic five-set final on Wednesday.

Throughout the match, del Potro did what he does best - pound heavy first serves and club ferocious forehands, a combination that Federer, the game's greatest tactician, managed to crack just twice.

"I played my best match of the tournament," del Potro said after the match.

"I served well and hit my forehand as hard as I can. We played a great match and I think I deserved to win in the end," he added.

Del Potro's shock victory over the number three seeded is even more remarkable considering his journey to the quarterfinals.

The big-serving Argentine had earlier defeated Dominic Theim, winning the most memorable match of the tournament so far this year.

In the fourth round clash against Thiem, Del Potro initially struggled and lost the first two sets with illness. But he stormed back to claim one of the most memorable comebacks in U.S. Open history and setting up a much-anticipated clash with the Swiss legend.

"I can't believe I will play in the semi-finals again after all my injuries, after all my surgeries. Especially to play here in New York, my favourite tournament," said the Argentine.

The result of the semi-finals denied Federer a shot at top-ranked Rafael Nadal in the semi-finals in a match that would have given him the chance to dethrone the Spaniard as World No. 1. Federer and Nadal have never played at Flushing Meadows.

Del Potro, world No. 28, will face Nadal in the semifinal on Friday.