MELBOURNE: Angelique Kerber had a straight-sets win for the first time in her first Australian Open title defense, starting her 6-0, 6-4 third-round victory with an eight-game streak against Kristyna Pliskova on Friday.
Top-ranked Kerber beat the other Pliskova twin, Karolina, in the final of the last U.S. Open to capture her second career Grand Slam title. Her first was here at Melbourne Park 12 months ago.
Kerber marked her 29th birthday on Wednesday with a second-round win over fellow German Carina Witthoeft, but said she didn't celebrate much between matches and hoped to do more at the end of the tournament.
She'll next play 35th-ranked CoCo Vandeweghe, who reached the fourth round in Australia for the first time with a -4, 3-6, 7-5 win over 2014 semifinalist Eugenie Bouchard.
"It will be tough," Kerber said. "I'm ready. I'm feeling good. I'm loving to play on this court."
Eighth-seeded Svetlana Kuznetsova was broken in the second and third sets when serving for the match before finally beating former No. 1-ranked Jelena Jankovic 6-4, 5-7, 9-7 in a 3-hour, 36-minute match.
Two-time major champion Kuznetsova will next play No. 24 Anastasia Pavlyuchenkova, who beat No. 11 Elina Svitolina 7-5, 4-6, 6-3.
Vandeweghe recovered from an early break in the third set in a tense win over Bouchard, who was ranked as high as No. 5 in 2014 when she reached the semifinals in Australia and France and the final at Wimbledon.
Vandeweghe converted her only break-point chance to take the first set but Bouchard leveled the match with two breaks in a dominant second set.
The 22-year-old Canadian broke to open the third set and appeared to be in control until Vandeweghe changed her approach.
"She started playing better and I got a little passive in my game plan and executing it — I was able to turn it around thankfully," Vandeweghe said.
After holding in the key eighth game of the third set, when she saved four break points in a game that went to deuce eight times, Vandeweghe had the benefit of serving first with no tiebreakers in the deciding set.
She easily held for a 6-5 lead and then, after Bouchard had a game point, went on a roll to close with a big backhand winner on her first match point.
Vandeweghe has reached the quarterfinals and the fourth round in the last two years at Wimbledon, but her run to the third round in Australia in 2016 was her best at any major not played on grass.
"It's just another opponent on the way to achieving my goal," Vandeweghe said of her win. "Anyway I could get it done — I just wanted to get the result. Achieved my goal."
Vandeweghe's new doubles partner, Martina Hingis, cheered her on throughout the match. Afterward, the American joked that Hingis might scold her for playing "too long to be fresh for the doubles."
Bouchard has been gradually improving her ranking in recent months. She hasn't gone past the third round of a Grand Slam tournament since slipping and falling in the locker room during the 2015 U.S. Open.