American teenager Caty McNally moved into the second round of the Volvo Car Open after No.10 seed Elena Rybakina retired from their match while trailing 6-4, due to illness.

In her tournament debut, 19-year-old McNally emerged victorious in a topsy-turvy opening set before the Kazakh deemed herself unable to continue. 118th-ranked McNally picked up her career-best win by ranking with the truncated victory over World No.23 Rybakina.

"I wish Elena a speedy recovery," McNally said on court, after the match. "She's obviously a great player, you can't get to [Rybakina's career-high] No.17 in the world without working so hard and being so good. I hope she gets better soon."

The match started with McNally holding a whopping ten break points in Rybakina's first two service games. McNally converted her fifth chance in the first game to go up an early break, but Rybakina saved another five in the third game to evade the double-break deficit.

The momentum flipped at that juncture, as Rybakina used powerful returns to break McNally twice in succession and open up a 4-2 lead, having won four games in a row. But the aggressive passes and groundstrokes suddenly clicked into gear for McNally, and she wrested command of the set to go on her own four-game streak and claim the set.

"No matter what, I'm always trying to play my game, come forward, be aggressive," McNally said. "On clay, you have to be a little more patient, and there's going to be bad bounces, and you just have to go with the flow."

After going down a set, Rybakina consulted with the medical trainers, and retired from the affair due to gastrointestinal illness, sending McNally into a second-round clash with either Anastasija Sevastova or Anastasia Potapova.

Other seeds who played during the second half of the day were more fortunate than Rybakina, including her 11th-seeded countrywoman Yulia Putintseva, who outlasted lucky loser Harriet Dart, 7-6(8), 6-4.

Putintseva was slated to face former Charleston champion Andrea Petkovic in the first round, but the German withdrew from their meeting due to a lower back injury.

Dart proved to be a formidable replacement as the Brit fended off one set point at 5-3 and two more at 6-5 to send the opening set into a tiebreak.

At last, Putintseva eked out that breaker to close out the one-set lead after over an hour of play, then gritted through the second set to line up a second-round encounter with another fellow Kazakh, Zarina Diyas.

No.17 seed Marie Bouzkova also had to fight back in a set before overcoming Timea Babos, 6-2, 7-5. Babos led 4-0 in the second set before Bouzkova won six of the last seven games to seal victory, although the Czech needed five match points in the final game before prevailing.

Bouzkova was promoted to a seeded position after No.4 seed and former Charleston champion Kiki Bertens withdrew from the main draw due to an Achilles injury. Bouzkova claimed just the second WTA-level clay-court win of her career with her victory over Babos.

No.15 seed Veronika Kudermetova made swifter passage into the second round, as she dispatched qualifier Desirae Krawczyk, 6-1, 6-2 in under an hour. Krawczyk, a top-tier doubles player ranked World No.24 in that discipline, is unranked in singles and was playing her first singles event of the season.