It looked like this finally might be the year.

Tennis titans Roger Federer and Rafael Nadal, who have faced each other 12 times in Grand Slam matches and 37 times overall, had yet to square off in a U.S. Open match. Nadal did his part Wednesday, defeating Andrey Rublev in quarterfinal play to take on the winner of Federer and Juan Martin del Potro.

Potro had other plans, though. The 24th-seeded Argentinian upset the 3rd-seeded Nadal, 7-5, 3-6, 7-6(8), 6-4, in the men’s singles quarterfinal at Arthur Ashe Stadium in New York to deny a Federer-Nadal semifinal.

“Rightfully so, I’m out of this tournament,” Federer said after the loss, via, “because I wasn’t good enough in my mind, in my body, and in my game. … If you’re missing all three, it’s going to be tough.”

Such an upset is nothing new for del Potro, though. The 28-year-old defeated Nadal in straight sets in the semifinals of the 2009 U.S. Open to prevent a Federer-Nadal final, then went on to stun Federer in the final to win the tournament.

Del Potro will attempt to do the reverse when he takes on Nadal in Friday’s semifinal. South Africa’s Kevin Anderson and Spain’s Pablo Carreno Busta will meet in the other semifinal.

Wednesday marked the sixth time Federer and Nadal — who have clashed at each of the other three majors — were one match away from facing each other at the U.S. Open.

Thumbnail photo via Geoff Burke/USA TODAY Sports Images