Nine years ago, the 20-year-old Juan Martín del Potro vanquished Roger Federer, then 28, in the U.S. Open men’s singles final for his first and only major title. Their five-set thriller, a seesaw affair that spanned more than four hours, still holds up as a U.S. Open epic and one of the great Grand Slam stunners. More significant even than his loss to Rafael Nadal in the Australian Open earlier that year—a result that brought Federer to tears—the 2009 U.S. Open defeat by del Potro caught the G.O.A.T. in the middle of a 41-match winning streak. What’s more: Federer was one victory away from becoming the first man since Bill Tilden in 1925 to conquer Flushing Meadows six years in a row.
On the other side of the net was del Potro, an Argentine who had announced himself as a major contender following wins that year against the reigning tennis kings Nadal and Andy Murray. This, despite his gangly 6-foot-6-inch build, which would seem better suited to running around screens on the basketball court than scooping up drop shots on a tennis court. But over the course of the fortnight, del Potro proved to be a quick and pliable enough mover with a sweeping forehand that boomed like a battleship gun. That flat, fatal stroke didn’t simply vault the sixth seed past the top-ranked Federer, it also helped del Potro topple Nadal in the semis to become the first man to beat them both at the same Grand Slam. It was a shocking turn of events that seemed to herald the dawn of a new era in men’s tennis, one that might soon see a fresh crop of young adults usurping the prevailing order.