Rafa Nadal retires with a knee injury in the US Open semifinal against Juan Martin del Potro

Juan Martín del Potro looking sensational when he won the first tie break

Juan Martín del Potro is back in a Grand Slam final after an absence of nine years, but only in the most unfortunate circumstances, since Rafael Nadal was forced to leave his US Open semifinal after two sets.

The 32-year-old Spaniard retired on Friday night to prevail over the Argentine 6-7, 2-6, with a recurrence of knee problems that prevented him from continuing.

The slower lanes, the oppressive weather and a long succession of hard combats badly affected Nadal, who also retired from the Australian Open quarter-finals in January when he was behind Marin Cilic.

Juan Martín del Potro looking sensational when he won the first tie break

Juan Martín del Potro looking sensational when he won the first tie break

Rafael Nadal looked frustrated as he had medical attention on his knee during the second set

Rafael Nadal looked frustrated as he had medical attention on his knee during the second set

Rafael Nadal looked frustrated as he had medical attention on his knee during the second set

Del Potro offered his sympathy to Nadal when the Spaniard decided to retire wounded

Del Potro offered his sympathy to Nadal when the Spaniard decided to retire wounded

Del Potro offered his sympathy to Nadal when the Spaniard decided to retire wounded

A dejected Nadal said later: "I had some problems during the tournament. I had a problem in the second or third game. Then I think it was a little better. I think it was 2-Everything in the first one, 15-Love, something like that in the first set, that I felt it.

"I told my box immediately that I felt something in the knee, after that, I was just trying to see if at some point things could improve during the game, but it was not the day.

"I expected everything I could." You can imagine it very difficult for me to say goodbye before the end of the game. But at some point you must make a decision. It was very difficult for me to continue playing at the same time in that way, having too much pain. "

Nadal could feel at least a little pleasure for Del Potro after all his struggles: "He's a player who went through a lot of problems during his career, as do I. I know how difficult this is, I know how much frustration there can be when you can not do it. what you want to do, happy for him, that he can return to his superior level, for him it will be enormous if he is able to win a Grand Slam again. "

The Argentine pursued each ball and forced Nadal to stand up for some epic rallies

The Argentine pursued each ball and forced Nadal to stand up for some epic rallies

The Argentine pursued each ball and forced Nadal to stand up for some epic rallies

Del Potro clenched his fist while a crowded crowd watched an excellent shock in the semifinal

Del Potro clenched his fist while a crowded crowd watched an excellent shock in the semifinal

Del Potro clenched his fist while a crowded crowd watched an excellent shock in the semifinal

He added that he was still happy to be doing what he is doing after a race that has seen so many ailments: "I am very competitive at the age of 32. Many people in this room, including myself, never thought that I would have 32 I will be here fighting for titles, fighting for the first place in the standings.

"All my career, everyone says that because of my style, I'll have a short career, I'm still here, I'm still here because I love what I do."

Del Potro knows all about the tribulations of injuries, his career has been so stunted by wrist problems since he won this title in 2009. It will be his first time in an important final since then, although he won the gold medal match at the Olympic Games in Rio, which he lost against Andy Murray.

The 29-year-old from Tandil was waiting for the winner of the second match between Novak Djokovic and Kei Nishikori.

He should have won the first set more easily, since he served for the first set at 5-4 and wasted two set points with unforced errors. It was the Spaniard who made the most mistakes in the tie-break, who lost 7-3.

Nadal fought hard in the first set but began to fight physically in the second

Nadal fought hard in the first set but began to fight physically in the second

Nadal fought hard in the first set but began to fight physically in the second

That seemed to deflate him, and there were already signs of discomfort in his right knee as he wore tape around, but only for two games before discarding it.

After not making much attempt to reach a discharge, he called the physiotherapist and took a medical waiting time of 2-1 in the second. The anguished look at his support box spoke of his concern.

Del Potro said later: "It's not the best way to win a game, I love playing against him, he's a fighter like that and I do not like to see him suffer." I'm sad for him.

"Anyway, the key was the first set, we both played good tennis, it was difficult, I did well in the tiebreak and I am very happy to be in the final one more time.

"It means a lot to me, I did not expect to reach another slam final, especially here in my favorite tournament, my best memories are in Flushing Meadows, in the final, when I beat Rafa and then Roger, I was a boy then, but now I'm much older. "

There was a silenced celebration of Del Potro after he won in unfortunate circumstances

There was a silenced celebration of Del Potro after he won in unfortunate circumstances

There was a silenced celebration of Del Potro after he won in unfortunate circumstances

Nadal recognized the crowd for his support and seemed distressed as he left

Nadal recognized the crowd for his support and seemed distressed as he left

Nadal recognized the crowd for his support and seemed distressed as he left

.