Italian defending champion Yannick Sener reached the quarter-finals of the Sofia Open by defeating Portuguese Nuno Borges in two sets without a response.
Sinner, the top seed in the tournament, won the first set 6-3.
The Italian player continued to dominate the match, ending the second set in his favour, 6-4, and proceeding to the quarter-finals.
In the quarter-finals, Sener will face Australian Alexander Vukic, who defeated Spain’s Fernando Verdasco in two sets for one, with details of 1-6, 6-4, 6-3.
Germany’s Jan-Lennard Struff qualified for the quarter-finals by defeating Frenchman Ugo Amber in two sets, 6-3, 6-1.
Denmark’s Holger Ronh also reached the quarter-finals by defeating Italian Lorenzo Sonego 6-7 (1-7), 6-4, 6-3.
Swiss Marc-Andrea Hussler blew up a big surprise following he ousted Spain’s Pablo Carreno Busta, the second seed in the Bulgarian championship, from the final price in two sets, 6-3, 3-6, 6-2 to cross to meet Poland’s Kamil Maijchak.