Juan Martin del Potro upset Roger Federer in the U.S. Open quarterfinals on Wednesday, denying the tournament its first–ever meeting between Rafael Nadal and Federer.
Federer and Nadal seemed to be on a collision course when they were drawn in the same half, but del Potro played spoiler. In a rematch of the 2009 final—which del Potro won in five sets—the Argentine kept Federer off-balance, winning a crucial third-set tiebreaker on his way to a 7-5, 3-6, 7-6(8), 6-4 victory.
Del Potro's shock victory over Federer, the tournament's No. 3 seed, is even more remarkable considering his journey to the quarterfinals. In the fourth round against Dominic Thiem, del Potro easily dropped the first two sets as he struggled with illness. But he stormed back to claim one of the most memorable comebacks in U.S. Open history and setting up a much-anticipated clash with Federer.
Federer was flat at times Wednesday, but del Potro played exceptionally well. In the fourth and final set, del Potro only hit one unforced error.
Del Potro, the tournament's No. 24 seed and the world No. 28, will face top-ranked Rafael Nadal in the semifinal on Friday. The winner will face either Pablo Carreño Busta or Kevin Anderson.
Del Potro, who has struggled with a series of injuries during his career, hadn't made a semifinal of a Grand Slam since 2013.
For Federer, the defeat marks the end of a highly successful Grand Slam season that saw him win both the Australian Open and Wimbledon. Federer has 19 career Grand Slam titles.