By JOHN PYE, AP Sports Writer

MELBOURNE, Australia (AP) — Sofia Kenin knew this would be a tough test at the Australian Open, a potentially early end to her first attempt to defend a Grand Slam title.

Upon realizing she probably would be playing big-hitting veteran Kaia Kanepi in the second round, Kenin acknowledged, she “maybe kind of broke down a little bit.”

Kenin was right to be worried. And, with Kanepi at her best, this one was over quickly. Delivering 10 aces, Kanepi powered her way past the No. 4-seeded Kenin, overwhelming the 2020 champion 6-3, 6-2 in just 64 minutes on Thursday.

“I obviously felt like I’m not there 100% — physically, mentally, my game. Everything just feels real off, obviously. It’s not good,” Kenin said at her news conference, where she wiped away tears.

“I mean, I just — I know I couldn’t really handle the pressure,” she said.

There’s very little that’s subtle about Kanepi’s game, and there wasn’t much nuance in the way she described her approach to this match: “I served really well today. I think this helped a lot. My game plan was to play aggressive, as I normally do.”

Yep, that pretty much sums it up.

This was certainly a significant upset based on rankings: Kanepi, an Estonian, is currently 65th. And based on past accomplishments: In addition to her title at Melbourne Park, Kenin reached the French Open final last year, while Kanepi is 0-6 in Grand Slam quarterfinals.

But the result did make some sense.

After all, Kanepi, 35, had beaten Kenin, 22, in their only previous matchup, part of why this was not a contest the American was looking forward to. Plus, Kanepi has been successful against some of the best on the biggest stages, with seven victories over Top 10 opponents at Grand Slam tournaments, including against then-No. 1 Simona Halep at the 2018 U.S. Open.

And then there was recent form.

Kenin walked off the court crying after a 6-2, 6-2 loss last week in a tuneup event at the site of the Australian Open and explained afterward that her left leg was sore. Kanepi, meanwhile, put an end to No. 7-ranked Aryna Sabalenka’s 15-match winning streak last week and entered Thursday having won 16 of her past 17 outings.

With serves topping 110 mph (175 kph), Kanepi saved all seven break points she faced. And she wound up with a 22-10 edge in winners.

“I couldn’t find my rhythm,” Kenin said. “I was obviously way too nervous.”

Her departure meant three of the top nine seeded women already were gone before midway through Day 4 at a Grand Slam tournament where routines have been disrupted by the pandemic, joining No. 8 Bianca Andreescu (the 2019 U.S. Open champion) and No. 9 Petra Kvitova (a two-time Wimbledon winner) on the sidelines.

Serena Williams remains the last woman to successfully defend a Grand Slam title — at Wimbledon way back in 2016.

Top-ranked Ash Barty did manage to avoid a surprise Thursday, but she blew a big lead in the second set and survived a shaky tiebreaker to get past Daria Gavrilova 6-1, 7-6 (7).

Barty is trying to become the first Australian to win the women’s title at Melbourne since Chris O’Neil in 1978.

“It’s a different challenge every single day,” Barty said. “It’s trying to be the best I can every single day, whatever that level is.”

Other winners included former No. 1 Karolina Pliskova and American Shelby Rogers.

Feliciano Lopez, at 39 the oldest player in the men’s draw, edged No. 31 Lorenzo Sonego 5-7, 3-6, 6-3, 7-5, 6-4. Lopez is appearing at his 75th consecutive Grand Slam singles event, a men’s record.

Barty lost only 10 points in the opening round, and her match against Gavrilova was equally lopsided until the wobbly finish. She led 5-2 in the second set but was broken twice serving for the victory.

In the tiebreaker Barty lost several ugly points. Gavrilova, a wild card, failed to convert two set points and committed unforced errors to end the final three rallies.

The two friends then shared a hug at the net.

“When you play another Aussie, rankings go out the window, experience goes out the window,” Barty said. “Typically you know each other so well. It’s always going to be a tricky match.”

Rogers reached the third round at the Australian Open for the first time by beating Olga Danilovic 6-2, 6-3. Rogers, 28, came into the tournament with a career record of 1-4 in Melbourne, but her ranking and fortunes have been on the rise of late.

She reached the quarterfinals at the U.S. Open for the first time last September, and her year-end ranking was a career-best No. 58. Rogers was sidelined for 14 months by a knee injury sustained in early 2018, and her ranking at the end of that year was 780th.

She had little trouble with Danilovic, a qualifier from Serbia ranked 183rd. The small crowd on Court 3 included Novak Djokovic, who sat behind the baseline shouting encouragement to his fellow Serb.

Pliskova, seeded sixth, advanced by beating American Danielle Collins 7-5, 6-2. Pliskova lost serve twice in a seesaw first set but pulled it out and then pulled away to beat Collins, a 2019 semifinalist at Melbourne Park.

Pliskova has won 65 matches in Grand Slams but is still seeking her first major title. She was runner-up to Angelique Kerber at the 2016 U.S. Open.

AP Sports Writers Steven Wine in Miami and Howard Fendrich in Washington contributed.

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