DOHA, Qatar (AP) Third-seeded Agnieszka Radwanska came through a tough first set before beating Monica Niculescu 7-5, 6-1 on Wednesday to reach the quarterfinals of the Qatar Open.

Radwanska, who was down a double break in the first set, struggled with her first serves. But as the match progressed, the Pole's superb shot-making gave Niculescu little chance of recovering.

''I think she has the best hands on tour, very tricky player and very uncomfortable to play against,'' Radwanska said of her Romanian opponent.

''I knew it was going to be tough and a long one. What can I say? She really made me play my best tennis, so I'm very happy to win that match in two sets.''

Radwanska next plays ninth-seeded Roberta Vinci of Italy, who defeated Turkish wildcard Cagla Buyukakcay 7-5, 6-1 in the last match of the day.

Also advancing from the third round was fourth-seeded Garbine Muguruza of Spain, who beat Timea Babos of Hungary 6-2, 7-5.

However, fifth-seeded Petra Kvitova of the Czech Republic lost 5-7, 6-2, 6-1 to Jelena Ostapenko of Latvia.

Kvitova, a two-time Wimbledon champion, came from 3-1 down to win the first set, but Ostapenko continued to play with confidence. She hit 28 winners before wrapping up the match in one hour and 56 minutes.

Ostapenko will next face China's Zheng Saisai, who continued her excellent form at the tournament by beating Canada's Eugenie Bouchard 7-6 (1), 6-1.

Zheng had beaten top-seeded Angelique Kerber on Tuesday.

Caroline Wozniacki of Denmark, seeded 13th, lost 7-5, 5-7, 6-3 to Elena Vesnina of Russia.