After 1:18 hours, the world number 14, who had not given a set in the entire tournament, converted his first match point.
German players did not start in Sofia.
In August, Sinner, then 19 years old, replaced the German Olympic champion Alexander Zverev as the youngest winner of an ATP tournament in the 500 category with his tournament victory in Washington DC.
Zverev pulls fans from their seats: The best rallies of the Laver Cup
