NEW YORK >> When Rafael Nadal finally finished a nearly five-hour climb into the U.S. Open semifinals, he thought backward as much as ahead.

His victory over Dominic Thiem reminded him of Wimbledon, where he outlasted Juan Martin del Potro in five sets in the quarterfinals before Novak Djokovic edged him in a 10-8 fifth set in the next round.

“When you win or when you lose like this,” Nadal said, “you come back home with the feeling that you did all the things that you can do.”

Now, Nadal might have to face those same two players again to defend his title in Flushing Meadows.

The top-ranked Spaniard plays third-seeded del Potro, and No. 6 seed Djokovic meets No. 21 Kei Nishikori in Friday’s other semifinal.

All four players have reached the U.S. Open final — only Nishikori hasn’t won it — to make this the first Grand Slam final four since the 2012 Australian Open in which all four players were past finalists.

Djokovic, bidding for his second straight major title, would seem to have the easier road to the final. He is 14-2 against Nishikori, including a victory in the quarterfinals at Wimbledon. He has won the last 13 meetings, such a run of dominance that the Japan native didn’t recall that he beat Djokovic in Flushing Meadows in the 2014 semifinals, adding that maybe he should rewatch the match.

“Yeah, for sure it’s going to give me good confidence,” Nishikori said, “even though I (don’t) remember.”

Nadal would figure to have a tougher time in his fourth meeting with del Potro in the last five Grand Slam tournaments. The two that preceded the Wimbledon classic were easier victories, a semifinal rout en route to the French Open title and a four-set victory in last year’s U.S. Open semifinals, when Nadal dominated the last three sets.

But del Potro was on fumes by then after winning his own memorable five-setter against Thiem in the fourth round and beating Roger Federer in the quarterfinals. And while he still had the devastating forehand that’s been one of tennis’ signature shots and carried him to the 2009 title, repeated wrist injuries had made him one dimensional on the backhand side.

Now, the Argentine has regained strength there, allowing him to change it up from slice to power.

“I feel that this tournament, Juan Martin is hitting a little bit bigger off his backhand. That can help him,” 2014 U.S. Open champion Marin Cilic said after Nishikori beat him Thursday.

“In the other case, Rafa had a tougher draw to go through the semis. But, you know, he’s got two days now to recover, so he’s going to be fresh. I don’t know. I would give slight advantage to Rafa, but I feel it’s going to be a great match.”

Nadal leads the series 11-5, though del Potro routed him in straight sets in the 2009 semifinals.

Both Nadal and Djokovic are in position for a two-slam season and a chance to inch closer to Federer’s men’s record of 20 Grand Slam titles. Nadal has 17, including three at the U.S. Open, and Djokovic could tie Pete Sampras for third all-time with 14 if he wins his third in Flushing Meadows.

This one, given the added difficulty created by unusually high heat and humidity, would certainly be meaningful.

“From my experience, and I can only talk about myself,” Djokovic said, “this has been definitely the toughest U.S. Open in the last, you know, 10 years that I have played in in terms of conditions.”