Top-seeded Jessica Pegula survived four match points to battle past 12th-seeded Victoria Azarenka 6-4, 3-6, 7-6 (7) on Friday in the quarterfinals of the Credit One Charleston (S.C.) Open.

Azarenka of Belarus also saved four match points but committed 12 double faults to none for Pegula, a top seed for only the sixth time in her career.

Pegula advances to a semifinal against fourth-seeded Daria Kasatkina, a Russian who converted 10 of 20 break points in topping Romania’s Jaqueline Cristian 6-7 (4), 6-2, 6-3 in a match lasting 2 hours, 42 minutes.

Danielle Collins won her 11th consecutive match to make it two Americans in the Charleston semifinals for the first time since sisters Venus and Serena Williams were in the final four 11 years ago. The unseeded Collins knocked off No. 11 Elise Mertens of Belgium 6-3, 6-4 in 1 hour and 24 minutes to advance to her 15th career tour-level semifinal.

Collins, a 30-year-old Floridian who is retiring at the end of the season, captured the Miami Open championship last week.

The other quarterfinal, third-seeded Maria Sakkari of Greece defeated ninth-seeded Veronika Kudermetova of Russia 6-2, 6-4, and will face Collins in the semifinals.

Copa Colsanitas

Eighth-seeded Kamilla Rakhimova of Russia was shut out in the first set, then rallied past fourth-seeded Cristina Bucsa of Spain 0-6, 6-4, 7-5 in the quarterfinals at Bogota, Columbia.

Sara Errani of Italy also got off to a slow start before eliminating Irina Bara of Romania 4-6, 6-2, 6-3 and advancing to the semifinals. Errani saved 17 of 23 break points while converting 8 of 20 opportunities.

In other quarterfinal matches Friday night, top-seeded Marie Bouzkova of the Czech Republic defeated seventh-seeded Laura Siegemund of Germany 2-6, 6-2, 7-5, and home-country favorite Camila Osorio, the sixth seed, rallied past second-seeded Tatjana Maria of Germany 1-6, 6-3, 6-3.

–Field Level Media