Novak Djokovic dropped the first set to a 22-year-old qualifier in his opening match at the BNP Paribas Open on Sunday night in Indian Wells, Calif., but the world's No. 1 player rebounded to dominate the next two sets and advance.
Djokovic beat American qualifier Bjorn Fratangelo, who is ranked 149th in the world, 2-6, 6-1, 6-2 in a second-round match.
Fratangelo's first-round win Friday was his first victory in four matches on the ATP World Tour, but he rushed to a 4-0 lead on his way to winning the first set Sunday.
Djokovic took control from there to improve his match record for the year to 17-1.
Djokovic's match followed Serena Williams' third-round victory on the women's side of the BNP Paribas Open. She also struggled a bit in the first round before finishing off a 7-6 (2), 6-0 victory over Yulia Putintseva.
Williams showed rust in the first set while playing just her second match since losing the Australian Open final six weeks ago. Putintseva, of Kazakhstan, was aggressive early, and that, combined with Williams' 29 unforced errors, led to a ragged start for the American.
Williams found her game in the second set and made quick work of Putintseva, winning 24 of the 30 points. She will face Kateryna Bondarenko of Ukraine in the fourth round.
Austrian Dominic Thiem was also tested but survived a strong effort from Slovakia qualifier Jozef Kovalik to advance.
Thiem, seeded 11th, delivered 10 aces while posting a 7-6 (4), 7-6 (3) victory over Kovalik in a one-hour, 47-minute match.
Thiem has won 21 matches this season, most of anyone of the ATP tour.
Seventh-seeded Jo-Wilfried Tsonga also advanced by winning a battle of Frenchmen, defeating qualifier Vincent Millot 7-5, 6-1. Tsonga won 12 of the final 15 games and needed just 70 minutes to finish off Millot.
In other men's action, Germany's Alexander Zverev defeated Bulgaria's Grigor Dimitrov 6-4, 3-6, 7-5; Spain's Roberto Bautista Agut advanced when Russia's Mikhail Youzhny retired; Adrian Mannarino posted a 6-1, 6-3 win over fellow Frenchman Benoit Paire; Japan's Kei Nishikori, the fifth seed, defeated Russia's Mikhail Kukushkin 6-3, 6-3; American Sam Querrey defeated Thiemo de Bakker of the Netherlands 7-6 (5), 6-4, and 16th-seeded Gilles Simon of France defeated Canada's Vasek Pospisil 1-6, 6-0, 6-1.
Radwanska, from Poland, advanced in convincing fashion while easily handling the serves of the Romanian.
Also, eighth-seeded Petra Kvitova of the Czech Republic defeated Sweden's Johanna Larsson 6-3, 4-6, 7-5; American qualifier Nicole Gibbs was a 6-0, 6-4 winner over Russia's Yaroslava Shvedova; Barbora Stryova of the Czech Republic topped qualifier Kurumi Nara of Japan 3-6, 6-1, 6-2; Jelena Jankovic of Serbia beat American CoCo Vandeweghe 6-0, 6-1; and Ukraine's Kateryna Bondarenko beat countrywoman Lesia Tsurenko 6-3, 4-6, 7-6 (7).