Roger Federer might be the favorite to win the 2017 U.S. Open, but his debut on Tuesday hardly went as planned. In the biggest surprise of the nascent tournament yet, 19-year-old Frances Tiafoe took Federer to the brink: It took the 19-time Grand Slam champion five sets to beat the young American 4-6, 6-2, 6-1, 1-6, 6-4.
Nobody really expected Federer to breeze his way to the final in Flushing Meadows, so perhaps it's a bit premature to push the panic button. He's still a clear favorite to win the tournament. But what in the world happened on Tuesday?