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Switzerland's Roger Federer and Spain's Rafael Nadal have played each other dozens of times through the years. Their rivalry has included memorable matches, including finals, at all but one of the world's Grand Slam championships.

They have never played each other at the U.S. Open.

Fans of the sport hoped that this year, two of the world's best would finally face off at Flushing Meadow in New York.

Those hopes ended Wednesday night, however.

Just hours after Nadal won a spot in the semifinal round of the tournament, Federer lost in four sets to Argentina's Juan Martin del Potro.

After his loss, Federer said of del Potro, "He came up with the goods when he needed to...and I helped him a little bit sometimes, too, maybe."

Federer also said that, unlike just about everyone else, he did not spend any time at all thinking about a possible matchup with Nadal.

This is the sixth time in which they were one game away from playing each other in New York. It happened in 2009, when del Potro himself beat Nadal in the semifinals, and then Federer in the final.

Federer entered the quarterfinals undefeated in Grand Slam play this season. He won titles at the Australian Open and Wimbledon. But he hurt his back at a tournament last month, which limited his preparation for the U.S. Open.

Before the U.S. Open began, Nadal was honest as can be when asked whether he hoped to face Federer. The answer was no, because he would prefer to play someone who is easier to beat.

Nadal will next face del Potro on Friday in the semifinal.

The other semifinal game includes two men who have never been this far at any major: Pablo Carreno Busta of Spain versus Kevin Anderson of South Africa.

On the women's side, the four remaining players are all Americans. It is the first time that has happened at the U.S. Open in 36 years. Venus Williams will play Sloane Stephens in one semifinal game, and Madison Keys will play CoCo Vandeweghe in the other.

And that's What's Trending Today...

I'm Caty Weaver.

The Associated Press reported this story. Ashley Thompson adapted it for Learning English. Hai Do was the editor.

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dozen - n. a group of 12 people or things

rivalry - n. a state or situation in which people or groups are competing with each other

match - n. a contest between two or more players or teams

face off - phrasal verb. to be involved or become involved in a conflict, dispute, or competition

matchup - n. a contest between athletes or sports teams.