Two-time Grand Slam singles winner Garbine Muguruza advanced to the second round of the US Open on Tuesday, the Spanish 10th seed easing past Japan's Nao Hibino in straight sets.
Muguruza, the 2016 French Open champion and 2017 Wimbledon winner, needed 1hr 30min to complete a 6-4, 6-4 victory over Hibino, the world number 78.
Muguruza will face Bulgaria's Tsvetana Pironkova in the next round. Pironkova advanced with a 6-2, 6-3 win over Russia's Liudmila Samsonova.
In other early women's matches, 16th seed Elise Mertens of Belgium cruised into the second round with a 6-2, 6-2 win over Germany's Laura Siegemund.
US hope Amanda Anisimova, seeded 22, also made sure of her place in the second round with a hard-fought win over Bulgaria's Viktoriya Tomova.
Anisimova prevailed 7-5, 7-5 in 1hr 27 minutes and now faces either Natalia Vikhlyantseva of Russia or compatriot Katrina Scott.