The quarterfinal lineup at the Credit One Charleston Open was completed on Thursday with wins by three of the top four seeds — and one big upset from Anna Kalinskaya over Australian Open champion Madison Keys.

Kalinskaya was a 6-2, 6-4 winner against No. 2 seed Keys in the first match of the night session inside Credit One Stadium, taking advantage of an erratic performance by the World No. 5 to score her first Top 10 victory in 10 months and advance to her second quarterfinal of the season. Keys hit 40 unforced errors in defeat, won less than 50% of points on her first serve, and converted just one of eight break point opportunities — all of which combined to help Kalinskaya level her all-time head-to-head record against Keys to 1-1. 

Charleston: Draws | Scores | Order of play

But Kalinskaya`s win over Keys wasn`t the only upset on paper in the Round of 16. Read on for more top stories from Thursday in Charleston.

Kalinskaya `needed this` amidst rough start: Kalinskaya, who peaked at a career-high ranking of No. 11 last October on the back of a 2024 season that saw her reach a WTA 1000 final in Dubai, a WTA 500 final in Berlin, and the second week of two Grand Slam events hadn`t yet recaptured that form in the first three months of 2025. After missing the Australian Open due to illness, she entered Charleston at 4-7 on the season and having won back-to-back matches at just one tournament, in Singapore in February (where she retired in the semifinals). 

But after securing an 11th career Top 10 win against Keys, the 26-year-old said the result was one she `needed.`

`This one is special. I needed this for my confidence. I had an unfortunate start to the year, but it`s nice to be back and playing at such a high level,` she said. `I think the key tonight was to change a little bit the rhythm; I did a few drop shots, especially in the first set.

`I didn`t want to go into very long rallies, because she`s a great player and she has unbelievable strong shots, so I tried to step in on the serve, be aggressive as much as I could, and be very consistent … to keep the level, and I think that was the key.`

Kalinskaya will next face 2020 Australian Open champion Sofia Kenin, who upset No. 5 seed Daria Kastkina in the nightcap, 6-3, 7-6(7).

Pegula keeps coasting: While her other top seeds have struggled in the first two rounds, there has been no such dram for No. 1 seed Pegula. After losing three games in her first round, Pegula lost just five against Ajla Tomljanovic to book a spot in her fifth quarterfinal of the season, 6-3, 6-2. 

The match was a far cry from the 6-1, 4-6, 6-3 semifinal that the two played in Austin last month, with Pegula winning five straight games in the middle of the match to pull away. 

She`ll take a perfect 6-0 head-to-head record against her next opponent, defending champion Danielle Collins, into the quarterfinals. Collins came from a break down in both sets to defeat No. 11 seed Jelena Ostapenko 7-5, 6-3 and win her eighth straight match in Charleston.

Zheng survives, Alexandrova tops Shnaider: Olympic champion Zheng Qinwen`s 13th consecutive clay-court win, meanwhile, didn`t come as easily. The No. 3 seed was forced to come from a break down in the final set en route to defeating No. 13 seed Elise Mertens, 6-3, 3-6, 6-3. 

She will next face No. 9 seed Ekaterina Alexandrova, who was a 6-1, 6-2 winner against No. 6 seed Diana Shnaider. Linz champion Alexandrova`s two wins this week snapped a four-match skid — which followed eight consecutive wins — dating back to the semifinals of the Qatar Total Open in February.