Austrian wild card Dominic Thiem advanced to the Round of 16 at the Winston-Salem (N.C.) Open when No. 1 seed Grigor Dimitrov of Bulgaria retired while leading their second-round match 6-0, 2-4 on Tuesday.

Dimitrov reportedly was struggling with his breathing during the second set and could not serve to start the seventh game. Before he retired, he had won 25 of 32 first-service points (78.1 percent), saved three of four break points and converted three of four break-point opportunities against Thiem, the former world No. 3.

No. 2 seed Botic van de Zandschulp got past fellow Dutchman Tallon Griekspoor 7-6 (5), 6-3. van de Zandschulp finished with a big enough edge in winners (27-17) to overcome committing more errors than Griekspoor (20-15).

Frenchman Richard Gasquet took down Italian fifth seed Lorenzo Musetti 7-6 (5), 4-6, 6-1 as part of a string of upsets. Gasquet’s countryman Adrian Mannarino knocked off No. 9 seed Emil Ruusuvuori of Finland 6-4, 6-1, American Steve Johnson beat Spanish 12th seed Pedro Martinez 7-6 (2), 6-2 and Serbia’s Laslo Djere rallied to top Portuguese 16th seed Joao Sousa 4-6, 6-3, 7-6 (5) in two hours and 48 minutes.

Other winners included fourth-seeded American Maxime Cressy, No. 8 seed Albert Ramos-Vinolas of Spain, No. 10 seed Benjamin Bonzi of France, No. 11 seed Ilya Ivashka of Belarus, No. 13 seed Jack Draper of Great Britain, No. 14 seed Lorenzo Sonego of Italy, No. 15 seed Jaume Munar of Spain, Swiss qualifier Marc-Andrea Huesler and Australian qualifier Jason Kubler.

–Field Level Media