Rafael Nadal hits a forehand against Juan Martin del Potro...

Rafael Nadal hits a forehand against Juan Martin del Potro during the first set of the U.S. Open men's semifinal match at the USTA Billie Jean King National Tennis Center on Thursday, Sept. 8, 2017. Credit: Newsday / J. Conrad Williams Jr.

So much of Rafael Nadal’s game is effort and passion, sure. Body and soul. He is known for his relentless work ethic. But throughout this U.S. Open, as Nadal worked toward Sunday’s championship match against unlikely finalist Kevin Anderson, he again has demonstrated a keen cognitive aspect.

Tennis balls are flying back and forth, like some metronome gone berserk, and Nadal is thinking on his (fast-moving) feet. In three early Open matches, and again in Friday’s semifinal against Juan Martin del Potro, Nadal appeared in significant danger in the opening sets. Each time — by applying perception, memory, judgment, reasoning — Nadal quickly flipped control to his side.

“Sometimes you need to lose [a set or several games] or you need to see things are not going well to take the position that, hey, maybe I change on this one,” he said.

Against del Potro, for instance, what appeared a reasonable opening strategy — hitting to del Potro’s weaker side, his backhand — brought nothing more than del Potro’s lead after the first set.

“I was wrong in the way I was trying to play, no?” Nadal said. “I started to understand a little bit better what I needed to do, to be a little bit more unpredictable, because he was waiting for me on his backhand side.”

Nadal began attacking the forehand down the line, opening the court, so that when he went back to del Potro’s backhand, he had del Potro on the run. “He arrived much more times running to his backhand then,” Nadal said. “And when he arrives running to his backhand, it’s completely different than when he is waiting for the ball there.”

Del Potro, appearing surrounded, struck only one backhand winner in the last three sets, when he won a total of five games. His plight was similar to those who had gone before him in the tournament: Serbia’s Dusan Lajovic, Japan’s Taro Daniel, Argentina’s Leonardo Mayer, Ukraine’s Alexandr Dolgopolov and Russia’s Andrey Rublev.

None of those fellows was seeded, and none ranked better than 53rd (the 19-year-old Rublev), but the 24th-seeded del Potro, when healthy, was good enough to have won the 2009 Open.

Nadal repeatedly insisted that the identity of his opponent was meaningless, that his chore was to simply play as well as he was practicing, which he said was “at a very, very high level.

“Of course if you practice well and you feel well, you have more chances to win matches,” he said. “But this 20, 30 percent is a big difference, because it’s about confidence. It’s about things that, when you are on the court, comes automatic. You don’t have to think about what you are doing at important moments. Things come straightaway.”

So Nadal will play for a major title for the 23rd time, in pursuit of his 16th Grand Slam trophy — second only to Roger Federer’s 19. And all of Nadal’s preparation, the instinctive hard-wiring that leads to in-match quick-thinking, will create more trouble today for Anderson, the 31-year-old South African experiencing his first major final in his 34th Slam appearance.

Anderson brings to the table his 6-8 frame, a big serve and modest ranking of No. 32. He is 0-and-2 lifetime vs. Nadal. In his fourth-round match, Anderson lost part of the middle toenail on his right foot and, after the match, had difficulty putting on a shoe.

“A lot of stopping and starting,” he said. “The toenails take a bit of a beating.” But with medical attention, he insisted there were no ill effects the rest of the way.

In January, Anderson was diagnosed with a tear in his right labrum, the ring of cartilage covering the ball-and-socket joint in his hip. There was the possibility of surgery, but Anderson overcame the injury with physical therapy. “I saw a lot of doctors,” he said. “If anybody has labrum issues and they’d like to talk to me about it, feel free. I learned a lot about it.”

He also learned this week that it was worth the effort to keep plugging. Here he is in a Grand Slam final, across the net from the world’s No. 1 player, hoping to give Nadal something to think about.

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