John Millman will be the first man to try to stop Alexander Zverev claiming back-to-back titles in Cologne, while Jannik Sinner also won.
Aryna Sabalenka will face Coco Gauff in the second round of the Ostrava Open after the 16-year-old American defeated Katerina Siniakova.
Anett Kontaveit, Sara Sorribes Tormo, Maria Sakkari and Barbora Krejcikova booked their places in the second round of the Ostrava Open.
A victory on home court at the St Petersburg Open means Andrey Rublev will scale new heights in the ATP rankings on Monday.
Alexander Zverev won the Cologne Indoors, his first 2020 title, as Felix Auger-Aliassime's wait for Tour glory goes on.