NEW HAVEN, Conn. — Top seed Agnieszka Radwanska overcame a slow start and breezed past Jelena Ostapenko 7-5, 6-1 on Tuesday night in the second round of the Connecticut Open.

Ostapenko had upset four-time New Haven champion Caroline Wozniacki in the first round and had a set point, leading the fourth-ranked player in the world 5-4. But Radwanska rallied to hold serve, then broke the 19-year-old from Latvia in the 11th game to take control of the match.

"I think I was just more patient and well, just two points better," said Radwanska, of Poland.

Before that match, the day belonged to the underdogs.

Kirsten Flipkens of Belgium became the fourth lucky loser this week to win a first-round match, beating Belinda Bencic of Switzerland 6-1, 4-6, 7-5.

She may have been the luckiest of them all.

The 30-year-old, who upset Venus Williams at the Olympics, had lost in the second round of qualifying in New Haven. But she was moved into the main draw after Ukrainian Lesia Tsurenko withdrew earlier in the day with a right knee injury.

Flipkens had been hanging around the Connecticut Tennis Center since that Saturday's defeat just to get some practice in before the U.S. Open. She signed in at 11:30 a.m. and found out at noon she would be playing a match.

"The first thing I had to do is get my rackets done," she said. "Luckily I had my match shirts and everything with me."

She dominated the first set over a rusty Bencic, who is coming off a left wrist injury and was playing her second competitive match since Wimbledon.

But the 19-year-old, who had been ranked as high as No. 7 in the world earlier this year, came back and was up 5-2 in the final set. It was a more poised Flipkens who won the next five games as Bencic lost control, slamming her racket on the court on more than one occasion as the match slipped away.

"I just knew I had to keep fighting, try to bring every ball back," Flipkens said. "I could feel a little that it was going to be mental at the end."

Another lucky loser, Johanna Larsson of Sweden, beat seventh-seeded Timea Bacsinszky of Switzerland 7-5, 6-2.

The 28-year-old got into the main draw when Russia's Svetlana Kuznetsova withdrew with a shoulder injury.

"You get a second chance and you just want to take it," she said. "I'm very happy that I made it happen today."

Larsson had lost every set in four previous meetings with Bacsinszky, who came in ranked No. 16 in the world.

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.

"We're focusing on the singles matches just before the U.S. Open and want to get some wins," Vesnina said. "So it's great that both of us are still in the draw and still winning and it's a good preparation for the U.S. Open, as well."

Vesnina will play Elina Svitolina of Ukraine, who won the last match of the day, 6-3, 6-1 over Evgenya Rodina of Russia. Svitolina is playing some of her best tennis coming off her upset of Serena Williams at the Olympics.