The third-seeded Musetti converted five of six break points while knocking off Ymer. Musetti won 26 of 34 (76.5 per cent) of his first-serve points.

Fourth-seeded Alexander Zverev of Germany rolled to a 6-3, 6-0 victory over Slovakia's Alex Molcan, while Germany's Yannick Hanfmann posted a 4-6, 6-2, 4-2 win when fifth-seeded Francisco Cerundolo of Argentina retired.

Number seven seed Alejandro Davidovich Fokina of Spain and number eight Miomir Kecmanovic of Serbia also prevailed.

Others winning first-round matches were Chile's Cristian Garin, France's Arthur Fils, Germany's Maximilian Marterer, Slovakia's Jozef Kovalik and China's Zhizhen Zhang.

Plava Laguna Croatia Open Umag

Zsombor Piros recorded a solid 6-3, 6-4 victory over fifth-seeded Christopher O'Connell in the first round at Umag on a day in which only two matches were completed due to rain.

Piros, from Hungary, won 30 of 39 (76.9 per cent) of his first-serve points while upsetting the Australian. Piros saved all four of his break points.

Seventh-seeded Italian Matteo Arnaldi registered a 6-3, 6-2 victory over qualifier Jesper de Jong of the Netherlands. Arnaldi also won 76.9 per cent (20 of 26) of his first-serve points.