We've all seen this before from Venus Williams. It's just been a while.

Serving well and hitting groundstrokes cleanly, Williams reached the U.S. Open quarterfinals for the first time since 2010, possibly setting up a showdown against her younger sister, by beating 19-year-old qualifier Anett Kontaveit of Estonia 6-2, 6-1 on Sunday.

It was about as quick and lopsided as a fourth-round Grand Slam match tends to get, taking only 50 minutes. The 23rd-seeded Williams won 21 of 25 first-serve points, faced merely one break point -- saving it, in the last game -- and committed just nine unforced errors, 12 fewer than her 152nd-ranked opponent.

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After that, Williams had a decision to make: How much of the next match in Arthur Ashe Stadium, Serena Williams vs. Madison Keys, was she going to watch? That winner would move on to face Venus in the round of eight.

"I get very nervous, because even if I have to play Serena, I still want her to win, so I have a hard time watching unless she's winning. Then it's easy to watch," said Venus, who won U.S. Open titles in 2000 and 2001, but had lost in the third round or earlier each of the past four years. "So it depends on how my nerves, are and I hope we can play in the quarterfinals."

Venus, 35, is about 15 months older than Serena, who headed into her all-American matchup against the 19th-seeded Keys hoping to keep alive her bid for a calendar-year Grand Slam, something last accomplished 27 years ago by Steffi Graf.

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"I'm so proud of Serena, and I think she's proud of me," Venus said. "We inspire each other."

Earlier Saturday, defending champion Marin Cilic overcame a tweaked right ankle thanks in large part to 23 aces, returning to the quarterfinals by eliminating 27th-ranked Jeremy Chardy of France 6-3, 2-6, 7-6 (2), 6-1.

The ninth-seeded Cilic rolled his ankle early in the second set but seemed to be moving fine by late in the third, which he ended with a down-the-line backhand passing winner on the run.

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"First couple games weren't easy. I was conscious about it," Cilic said about his ankle. "It was causing a bit of trouble."

But when ace after ace arrives, movement isn't as important.

"They key today," Cilic said, "was finding my rhythm on the serve."

Now there's an understatement. He smacked serves at up to 132 mph, relying on that shot to carry him in the pivotal third-set tiebreaker, when Cilic hit four serves: 120 mph ace, 131 mph ace, 123 mph ace, 112 mph ace.

Next up for the Croatian is a matchup against 19th-seeded Jo-Wilfried Tsonga of France, whose serve has been just as good, if not better, so far. Through four matches, Tsonga has not only never dropped a set, he hasn't even been broken once, saving the only two break points he's faced.

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Tsonga didn't have to deal with any break chances Sunday, defeating another Frenchman, 41st-ranked Benoit Paire, 6-4, 6-3, 6-4.

The 2008 Australian Open runner-up, Tsonga has reached at least the semifinals at every major tournament except the U.S. Open.