Serena Williams and Maria Sharapova have confirmed their quarterfinal date at the Australian Open, each advancing in straight sets on Sunday to ensure a rematch in Melbourne Park between last year's finalists.

Fifth-seeded Sharapova fired a career-high 21 aces and hit 58 winners in her 7-5, 7-5 win over Belinda Bencic in the first match of the day on Rod Laver Arena, converting her second match point with a successful challenge after her forehand was initially called long.

Six-time champion Williams followed it up with a 55-minute, 6-2, 6-1 win over Margarita Gasparyan.

Margaret Court, the Australian great who won 24 Grand Slam singles titles and has a court named in her honor at Melbourne Park, was in the crowd watching Williams reach the quarterfinals of the season's first major for the 10th time.

Williams, with 21 majors, has won 18 of their 20 matches, including 17 in a row.

Under bright sunshine after the roof was opened following morning rain, Williams was broken in the opening game — her only point coming from an ace — but quickly found her groove and won 12 of the next 14.

The 34-year-old Williams was so close to a calendar-year Grand Slam in 2015, winning the Australian, French and Wimbledon titles before her upset semifinal loss to Roberta Vinci at the U.S. Open.

"Well, gosh, I didn't know she was here, I feel honored to be able to play in front of her," Williams said when told Court was in the stands, then looked up to the VIP area and added: "Thank you."

"Obviously 24 is close, but yet it's so far away," Williams said of Court's career record. "I never play thinking I want to be (equal) with the great Margaret Court, I just play just want to win a Grand Slam and that's it. So here I am, I'm just playing for me."

As for Sharapova, Williams said she hadn't looked at the draw to see who would be next, but noted that the five-time major winner "had a really good win today ... it will be a good match." Williams said she felt confident in her game regardless of who she was playing.

Sharapova won consecutive matches against Williams in 2004 at Wimbledon and the season-ending championships, but hasn't won since. It's a statistic she tries to block from her mind.

"It's not like I think about what I can do worse. You're always trying to improve," she said. "I got myself into the quarterfinal of a Grand Slam. There is no reason I shouldn't be looking to improve and to getting my game in a better position than any other previous round. It's only going to be tougher, especially against Serena.

"I look forward to playing the best in the world and that's what she's proven in the last year."

Sharapova, the 2008 champion and four-time finalist, had to play under an indoor match because play started while it was lightly raining, but the roof was open for Williams.

Kei Nishikori was the first male player through to the quarterfinals, beating No. 9-seeded Jo-Wilfried Tsonga 6-4, 6-2, 6-4 in front of a partisan crowd filled with flag-waving Japanese fans.

The seventh-seeded Nishikori, the 2014 U.S. Open finalist, also reached the quarterfinals at the Australian Open last year and in 2012.