Nadal will meet Kevin Anderson who also came back from losing the first set to win his semifinal match.
Rafael Nadal moved closer to a 16th grand slam title when he recovered from a first set wobble to beat Argentine Juan Martin del Potro 4-6, 6-0, 6-3, 6-2 in the US Open semifinals on Friday.
The World number one struggled to handle his opponent's serve and huge forehand in the opening set before finding his stride to set up a title decider with South Africa's Kevin Anderson on Sunday.
"It's been an amazing season for me and I'm so happy to get a chance to fight for another title after a couple of seasons with injury troubles," said Nadal, who won a record-extending 10th French Open title in June.
"It means a lot to me. I had to change a couple of things after the first set because I was playing on his backhand too much and he was waiting for me there. So I tried to move him around more and be more unpredictable. I was not playing bad in the first set but I lost it so some things had to change."
Del Potro was dominant early, hammering Nadal with his forehand and serving strongly to put the Spaniard in full-defence mode.
The Argentine closed out the first set with a lightning quick forehand.
Nadal, in response, broke Del Potro three times in succession and conceding only one unforced error to dole out a bagel in the second set.
The Spaniard maintained the pressure, a forehand winner down the line capturing an early break and a 2-0 lead in third set.
Having lost nine consecutive games, Del Potro finally held serve to trail 3-1 and started hitting big forehands again.
But Nadal stayed in control and sealed the set with a fine overhead.
An exhausted Del Potro began netting easy shots and again found himself down an early break in the fourth set.
The 31-year-old Nadal, with his teeth firmly in his prey, showcased his defensive class to turn things around on match point and set up a strong chance for more grand slam silverware.
Here is how it happened:
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