Rafa Nadal – the French Open winner – will contest his third slam final of the year against South Africa’s Kevin Anderson, and the 23rd of his illustrious career.
The Spaniard won nine games in a row at one stage on his way to a 4-6 6-0 6-3 6-2 victory in the second semi-final.
Nadal, 31, will try for a third US Open and 16th Grand Slam title on Sunday, against a surprise opponent.
South Africa’s Anderson, 31, beat Spaniard Pablo Carreno Busta 4-6 7-5 6-3 6-4 earlier on Arthur Ashe Stadium.
At 32 in the world, Anderson is the lowest-ranked man to reach a US Open singles final since the ranking system was introduced in 1973.
He faces a huge challenge against Nadal, who has a 4-0 record in their head-to-head and grew stronger as the match wore on against a tired Del Potro.
But there are more important things to the 15-time major champion, given the 31-year-old’s run of injuries in recent years.
“For me what is more important, more than win slams is be happy. I am happy if I am healthy and happy, if I feel competitive in the most of the weeks that I am playing, and that’s what happened this year,” Nadal, who has two US Open crowns to his name, said.
“So I am very happy about what happened, very happy to win Monte-Carlo, Barcelona, Madrid and Roland Garros. I am very happy to be in the final here in the US Open.
The last time Nadal lost a Grand Slam semi-final was against Del Potro on the same court eight years ago, and he was not about to endure a repeat performance.
After losing a tight first set, the Spaniard hit a rich vein of form, dropping just five more games, dominating on serve and ending the match with 25 forehand winners.
“I changed a couple of things after the first set,” added Nadal.
“I was playing too much to his backhand and I knew that I had to change and move him more and be more unpredictable. It worked really well and I am very happy.”
Del Potro, roared on by the Argentine fans who have given him loud support throughout this US Open, gathered himself to win a tight first set, before running out of steam.
The 24th seed coped superbly in the early stages as Nadal pummelled his weaker backhand wing, winning the cross-court battle and, thanks to a net cord on break point, with it the set.