After losing the first three matches of his comeback this year, he has gone on to reach the quarter-finals at Roland Garros, lose to Nadal in the semi-finals in Rome and in the Queen's final to Cilic, before beating Kevin Anderson in the Wimbledon final.
It was Nadal who succeeded Del Potro as the US Open champion in 2010.
Nadal, a 17-time Grand Slam champion, mentioned retirement to the chair umpire midway through the second set, then threw in the towel after dropping the set.
"Well of course it's not the best way to win a match".
'I love to play against Rafa because he's the biggest fighter in this sport.
When Rafael Nadal finally finished a almost five-hour climb into the U.S. Open semifinals, he thought backward as much as ahead. While an nearly five hour quarter-final victory over Dominic Thiem, it would be fair to state concerns over the winning player in their subsequent match, but the quirks of the US Open schedule mean that the Spaniard will have had nearly 72 hours to recover from these exertions - virtually unheard of recovery time in the latter stages of professional tennis tournaments. He has proven in the past that he can match Nadal on hard courts and assuming he can get his forehand firing, he can nick this one in four sets.
Del Potro, whose own injury troubles have been well-documented, will therefore get a chance to repeat his 2009 triumph in NY.
Former President Obama delivers speech at University of IL
Meanwhile, Michelle Obama is also stepping up her political involvement ahead of the November midterm election. The entire speech can be viewed below, live at Noon EST.
"I didn't expect to get to another Grand Slam final in my favourite tournament".
Nishikori's take: "I don't have great record against Novak, but always it's been a tough match last couple of years.
But the good thing is I know how I have to work to be better as soon as possible because we have a lot of experience on that", Nadal said. But at some point, you have to take a position.
The first signs of trouble with Nadal's knee came after the seventh game of the first set, when the Spaniard called the trainer to have his right knee taped just below the kneecap - the same place he had it taped throughout his third-round match against Karen Khachanov, a four-setter that lasted 4 hours 23 minutes. I know how much frustration there can be when you can't do the thing that you want to do. He avoided comparing it to his previous knee injury.
"It's not a match when one is playing and the other is at the side of the court", Nadal added.
Still, he retains the No. 1 ranking no matter if del Potro or Djokovic lifts the U.S. Open trophy Sunday. He'll attempt to win his second U.S. Open title nine years after he defeated Rafa Nadal then Roger Federer to win his only career major title. "I had my biggest memories on the tennis court playing on this court ... but I was a kid". The big question now is how much is left in the tank of the 32-year-old's legs, especially after his mammoth quarter-final with Dominic Thiem.
Del Potro knows all about injury tribulations, his career so badly stunted by wrist problems since winning this title in 2009.