The 20-year-old Italian jumped to No. 31 after upsetting top-seeded Carlos Alcaraz 6-4, 6-7 (6), 6-4 in the final of the Hamburg European Open on Sunday for his first tour-level title.
Musetti will next play fellow Italian Marco Cecchinato.
Fifth-seeded Alex Molcan of Slovakia advanced with a 6-2, 7-6 (2) victory over Duje Ajdukovic of Croatia while sixth-seeded German Daniel Altmaier was upset by French qualifier Corentin Moutet 6-4, 6-2.
In an all-Argentine opening round, Facundo Bagnis defeated Tomas Martin Etcheverry 7-5, 6-3. Federico Delbonis, also of Argentina, was knocked out by Slovakian lucky loser Norbert Gombos 6-4, 5-7, 6-4.