An amazing upset at Flushing Meadows on Monday evening: Big-hitting Argentine Juan Martin del Potro has defeated Roger Federer to take the U.S. Open men’s tennis championship. The No. 6-seeded del Potro stunned the No. 1 defending champion, who was seeking his record 16th Grand Slam title, in five sets, 3-6, 7-6, 4-6, 7-6, 6-2. The victory is the 20-year-old del Potro’s first Grand Slam title and breaks Federer’s streak of five straight U.S. Open championships. Del Potro reached the final by defeating Rafael Nadal 6-2, 6-2, 6-2.