Former world number one and 24th seed Garbine Muguruza has crashed out of the US Open in the first round, losing 2-6, 6-1, 6-3 to the USA's Alison Riske. The Spaniard had also fallen at the first hurdle of Wimbledon in July, losing in straight sets to Beatriz Haddad Maia. Top seed and defending champion Naomi Osaka had her own scares against Anna Blinkova, falling behind 1-4 in the first set before winning five games in a row, and losing a match point in the second set before moving on to a 6-4, 6-7(5), 6-2 victory. "I don't think I've ever been this nervous in my life," she said in an on-court interview. "I don't think I ever really found my rhythm, but I just fought as hard as I can." Osaka chose to look on the bright side of her unexpectedly competitive match against the world number 84. "It helps me a lot because I learn from the tougher matches. It helps me prepare to have to adjust my game plan throughout the match." Wimbledon champion Simona Halep, seeded fourth, had to go the distance to beat Nicole Gibbs, winning 6-3, 3-6, 6-2; it was the Romanian's first victory at Flushing Meadows since 2016. Caroline Wozniacki, the 19th seed, lost the first set to Yafan Wang of China, but came back to win 1-6, 7-5, 6-3. Sixth seed Petra Kvitova had a rather more straightforward time of it, beating Czech compatriot Denisa Allertova 6-2, 6-4; Switzerland's Belinda Bencic, seeded 13th, also had a routine win, beating Mandy Minella of Luxembourg 6-3, 6-2. Rogers Cup champion Bianca Andreescu beat qualifier Katie Volynets 6-2, 6-4, saving four out of five break points in the process. Former French Open champion Jelena Ostapenko pulled off a win against the in-form Aleksandra Krunic, triumphing 6-3, 7-6(7). Julia Goerges, the 26th seed, also required a tie-break to win against Natalia Vikhlyantseva – but theirs was in the final set, with the German coming through 1-6, 6-1, 7-6(1).