Garbine Muguruza, the reigning French Open champion and the world No. 3, was upset in the second round of the U.S. Open by Anastasija Sevastova on Wednesday.
Sevastova, 26, prevailed 7-5, 6-4 to advance to the third round of a Grand Slam for just the second time in her career. She had never advanced past the second round of the U.S. Open.
Muguruza's defeat concludes a roller-coaster summer for the Spaniard, who won the French Open in June but crashed out of Wimbledon in the second round.
Sevastova broke Muguruza three times in the opening set, including at 4-5 when Muguruza had a chance to lock up the first set.