TORONTO, Canada (AFP) — Top-ranked Aryna Sabalenka advanced to the fourth round of the WTA Toronto Masters on Thursday by defeating China’s Zhang Shuai 6-3, 6-4.

The 28-year-old reigning US Open champion from Belarus, a four-time Grand Slam winner, dropped only seven points on her first serve to advance in 76 minutes.

Sabalenka, with a 38-6 record and three titles this year, struggled to find a rhythm in her return games early.

“I was trying to step in, and then I would step back and nothing really clicked,” she said.

“In the end, I finally started moving a little bit better and finding my rhythm, so I’m really happy at the end; it really clicked.”

Sabalenka said she enjoys being on top of the rankings, a spot she has held for more than 100 weeks in her career.

“I love it. It just means I’m ahead, and they have to come up with something crazy to play such tennis, and I’m only getting better from that,” Sabalenka said.

“I enjoy being the one being chased. It’s really fun. It’s a tough challenge, but I love to go through it, and it makes me stronger.”

Sabalenka next plays against Russian 16th seed Ekaterina Alexandrova, who eliminated Australian Talia Gibson 5-7, 6-1, 6-3.

Sabalenka leads their personal rivalry 5-4 thanks to a victory this year on Berlin grass, but Alexandrova won their most recent hardcourt match in a third-set tiebreaker last year at Doha.

“Great player. Super aggressive. Fast game. Always have to stay low,” Sabalenka said. “It’s always great battles and a lot of things to work on.”

American third seed Jessica Pegula advanced to the round of 16 by defeating Uzbekistan’s Kamilla Rakhimova 6-4, 6-0 in 68 minutes.

Pegula will play for a quarterfinal berth against Russian 15th seed Diana Shnaider, who eliminated compatriot Anna Kalinskaya 6-3, 6-3 in 77 minutes.

Polish seventh seed Iga Swiatek advanced with a 6-2, 6-1 romp over Swiss Viktorija Golubic in 66 minutes, landing 18 winners and losing only 14 points on her serve.

“For sure it was a good day, and I’m really happy with the way I played,” Swiatek said.

Swiatek countered Golubic’s versatile shots by forcing the match tempo.

“I played back her slice pretty well so the change of rhythm didn’t bother me that much,” Swiatek said. “I tried to pick the right balls to attack because I was controlling the pace. It was just about the decision-making.”