Roberto Bautista Agut brushed aside Mikhail Kukushkin at the Swiss Indoors Basel on Monday, but Denis Shapovalov had to work hard to get past Yuichi Sugita.
Bautista Agut, seeded sixth for the ATP 500 competition at St. Jakobshalle, thrashed his Kazakh opponent 6-0 6-3 in less than hour to advance to the second round, where he will face Ryan Harrison or Alexandr Dolgopolov.
Rising Canadian star Shapovalov endured a more difficult passage, coming from a set down to get past Japan's Sugita 4-6 6-2 7-6 (7-3).
The 18-year-old's victory saw him qualify for next month's inaugural Next Gen ATP Finals for players aged 21 and under.
In the other matches on Monday, Hyeon Chung ousted Paolo Lorenzi 6-3 6-1, while Robin Haase saw off home-crowd favourite Marco Chiudinelli 6-2 7-6 (7-3).
There were some famous faces in the stands on day one, as Roger Federer and his wife Mirka took in the action ahead of the Swiss great joining the fray against wild card Frances Tiafoe on Tuesday.