MELBOURNE, Australia (AP) — The Latest on the Australian Open (all times local):

3:55 p.m.

Roger Federer took another step toward a 21st Grand Slam singles title with a routine 6-3, 6-2, 6-2 win over Steve Johnson at Rod Laver Arena.

Federer, playing his first tournament of the season, wasn't troubled in his match with the American as he seeks his seventh Australian title. He won his first in Melbourne in 2004.

Two-time Wimbledon winner Petra Kvitova is also through to the second round after beating Katerina Siniakova 6-1, 6-0.

Kvitova lost the final here last year to Naomi Osaka. Afternoon rain suspended play on outside courts but matches continued on the three stadiums with roofs.

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3:10 p.m.

Former No. 1-ranked Caroline Wozniacki beat Kristie Ahn 6-1, 6-3 in the first round of the Australian Open, the last tournament of her professional career.

Wozniacki has announced she will retire after the Australian Open, where she won her first major title in 2018. There were several rain delays in the mid-afternoon, prompting organizers to close the roof on each of the three man show courts. Play was suspended on outside courts when heavy rain fell shortly after the first delay.

Rain is on the forecast for the first two days of the Australian Open.

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2:30 p.m.

No. 13-seeded Denis Shapovalov is out of the Australian Open after losing in four sets to Marton Fucsovics. The 20-year-old Canadian lost 6-3, 7-6 (7), 6-1, 7-6 (3). Shapovalov berated the umpire and received a code violation during his ill-tempered match on Margaret Court Arena. The blowup came after the third set.

After throwing his racket, Shapovalov was given the code violation that triggered his outburst.

“I didn't break it. If I break it, 100% code me,” Shapovalov yelled at umpire Renaud Lichtenstein. “You're not doing your job. You're just finding reasons to code me.”

Fucsovics also beat the 13th seed last year at Melbourne Park, that time Sam Querrey in the second round.

“Usually this is not a lucky number, but for me, my favorite number,” he said. “I played some of my best tennis today. Everything was working well.”

Not long after Shapovalov's exit, rain caused the suspension of matches around the grounds.

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2 p.m.

Serena Williams won the first set in 19 minutes and had a momentary lapse at the start of the second but completed a 6-0, 6-3 win over Anastasia Potapova. The eighth-seeded Williams is attempting to win her record 24th Grand Slam singles title. Williams had her service broken in the second game of the second set after cruising through the first. But she broke Potapova's serve two games later, her fifth successful break in six attempts.

Williams won last week's Auckland tournament.

“I hadn't been able to win as a mom, so it was nice to finally be able to win a tournament with a 2-year-old now," Williams said. “”I've been pretty close but it was special for me and for her. I hope for her."

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12:40 p.m.

Defending champion Naomi Osaka has won the opening match in Rod Laver Arena, reeling off the last four games after dropping serve for the only time to beat Marie Bouzkova 6-2, 6-4.

Osaka is aiming to be only the ninth woman to successfully defend the Australian Open title. She wasn't able to do that at the U.S. Open last year, when she lost in the fourth round a year after winning her first major title in New York, but says she learned some valuable lessons there. “Definitely, it was really tough for me trying to control my nerves. I’m really glad I was able to finish it in two," Osaka said.

She was given the first match on the main court at Melbourne Park on a day when former champions Serena Williams, Novak Djokovic and Roger Federer will also feature on Rod Laver.

“Thanks everyone. You probably didn’t come for me, but thanks for filling up the stadium,” she said.

Osaka hit 29 winners and 28 unforced errors, pushing No. 59-ranked Bouzkova around with some heavy ground strokes.

Other seeded players advancing included No. 13 Petra Martic and No. 14 Sofia Kenin.

Martic had a 6-3, 6-0 win over Christina McHale and Kenin beat Italian qualifier Martina Trevisan 6-2, 6-4.

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11:55 a.m.

Radu Albot has withdrawn from the Australian Open before his scheduled first-round match against No. 32-seeded Milos Raonic and will be replaced by lucky loser Lorenzo Giustino, an Italian who is ranked 150th. Albot, who finished 2019 ranked 46th, played for Moldova at the season-opening ATP Cup and lost his three singles matches to Daniel Evans, Grigor Dimitrov and David Goffin in the group stage. Organizers did not immediately release details of Albot's injury.

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11 a.m.

Cloudy skies and the threat of rain greeted players and spectators on Day 1 at the Australian Open, the first Grand Slam tournament of the decade.

Defending champion Naomi Osaka was playing the opening match at Rod Laver Arena against Marie Bouzkova. Following that, Serena Williams begins her quest for a record 24th Grand Slam singles title.

Defending champion Novak Djokovic begins his chase for an eighth Australian Open title and third-seeded Roger Federer starts his campaign for a men's-leading 21st Grand Slam singles title, both in later matches at Rod Laver.

Night matches feature No. 1-ranked Ash Barty, who is hoping to become the first Australian woman to win her home major since 1978, and an American veteran playing a rising star — Venus Williams vs. Coco Gauff.

Weather forecasters are saying there's a 100% chance of showers along with the possibility of thunderstorms. A high temperature of 21 Celsius (70 Fahrenheit) is expected.

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