Top-seed Agnieszka Radwanska has breezed past 19-year-old Jelena Ostapenko 7-5 6-1 in the second round of the Connecticut Open.
The fourth-ranked player in the world trailed 4-5 and faced a set point before taking control of the Tuesday night match.
Olympic doubles champions Ekaterina Makarova and Elena Vesnina of Russia became the first players to advance to the third round of the singles competition.
Vesnina was leading Anett Kontaveit 6-4 1-0 when the 20-year-old Estonian withdrew with a left thigh injury. Makarova beat qualifier Anatasija Sevastova of Latvia 6-3 6-2.
Belgian Kirsten Flipkens added to an already memorable northern summer by beating Belinda Bencic of Switzerland 6-1 4-6 7-5.
Flipkens, who upset Venus Williams at the Olympics, had lost in the second round of qualifying in New Haven but was moved into the main draw after Ukrainian Lesia Tsurenko withdrew earlier in the day with a right knee injury.