Paris: Former French Open champion Stan Wawrinka posted another solid performance to reach the third round at the French Open on Thursday.
Yet to drop a set at the tournament so far, the three-time Grand Slam champion played aggressively and close to the lines throughout, hitting 45 winners to beat Alexandr Dolgopolov 6-4, 7-6 (5), 7-5.
"The most important thing for me is the way I play," said Wawrinka, who beat Novak Djokovic in the final two years ago. "It was a difficult challenge because he is varying and mixing his shots well."
Dolgopolov made only 18 unforced errors but Wawrinka played a flawless baseline game, punctuated by some superb shots.
"It was a very, very good match," said Wawrinka, who will next take on Italian Fabio Fognini. "Again a tough match. Kind of player like Dolgopolov, unpredictable."
Earlier, Karen Khachanov advanced to the third round of a Grand Slam tournament for the first time by upsetting 13th-seeded Tomas Berdych 7-5, 6-4, 6-4. The 21-year-old Russian had 12 aces against Berdych and set up a big server contest. He will take on No. 21 seed John Isner for a spot in the fourth round. The American player hit 21 aces in his 6-3, 7-6 (3), 7-6 (2) victory over Paolo Lorenzi.
On a sunny day at the clay-court Grand Slam, there was plenty of drama and tears on court 2, where Nicolas Almagro retired early in the third set against No. 29 seed Juan Martin Del Potro because of an injured left knee.
Del Potro, the 2009 U.S. Open champion, also had physical problems on his upper right leg during the match. He won the first set 6-3, then Almagro took the second by the same score, and it was 1-all in the third when the match ended.
Almagro's left knee was taped by a trainer. Then he stopped playing and rested both hands on his knees and shook his head. Then he held his hands on his head and began crying, before falling onto his back. Del Potro climbed over the net and walked over to check on Almagro.
In the women's draw, Agnieszka Radwanska won back-to-back matches for the first time since reaching the final in Sydney in January.
Radwanska, seeded ninth at the French Open, beat qualifier Alison Van Uytvanck 6-7 (3), 6-2, 6-3.
Earlier in the clay-court season, Radwanska has missed the Madrid and Rome tournaments because of a right foot injury.
"I have been struggling with my health for a couple of weeks," Radwanska said. "I only had a week practice, so I am just very happy to be in the third round."
Among the women also advancing to the third round were No. 5 seed Elina Svitolina and No. 14 Elena Vesnina.