– Serena Williams equaled her most lopsided victory in 30 professional meetings with sister Venus, winning 6-1, 6-2 on Friday night in the third round of the U.S. Open.

Serena shook off an early ankle injury to win seven consecutive games and seize control in perhaps her most dominant performance since giving birth to her daughter a year ago Saturday.

The sisters' earliest meeting in a Grand Slam tournament in 20 years was over early, with Venus unable to do anything to blunt Serena's power, even after the crowd tried desperately to get behind her early in the second set.

"It's not easy," Serena said, despite how easy it looked in a match that lasted just 1 hour, 12 minutes.

"She's my best friend. She means the world to me. Every time she loses, I feel like I do. It's not very easy, but it's a tournament. We know there's more to life than just playing each other and playing tennis."

They hadn't played this early in a Grand Slam since Venus won in the second round of the 1998 Australian Open in their first meeting as pros, and only once over the next two decades had either won so decisively. Serena won by the same score in a semifinal victory in Charleston, S.C., in 2013.

"I think it's the best match she's ever played against me," Venus said. "I don't think I did a lot wrong. But she just did everything right."

Serena, the No. 17 seed, will face Kaia Kanepi, who knocked out top-ranked Simona Halep in the first round.

Serena, who turns 37 next month, leads the series 18-12 with her sister, 11-5 in Grand Slam tournaments. But this one wasn't expected to be so easy, not with Serena still working her way back into form after returning to action in the spring.

But this was the type of tennis that has brought her to 23 Grand Slam singles titles, the ability to pound balls all over the court and chase down the rare shots that looked like they might get past her.

"This was my best match since I returned," he said. "I worked for it. I worked really hard these last three or four months. That's life, you have to keep working hard no matter ups or downs you have. That's what I've been doing."

She pounded 10 aces to just one for Venus, the No. 16 seed who was perhaps a little drained after two tough matches to begin the tournament, including a three-setter against 2004 U.S. Open champion Svetlana Kuznetsova in her opener.

"I mean, she played so well, I never got to really even touch any balls," said Venus, a semifinalist at the U.S. Open last year. "When your opponent plays like that, it's not really anything to be upset about."

On the men's side, top-ranked and defending champion Rafael Nadal overcame a shaky start Friday and used his customary relentless style to wear down No. 27 seed Karen Khachanov physically and mentally, eventually getting to the fourth round with an entertaining and back-and-forth 5-7, 7-5, 7-6 (7), 7-6 (3) victory that took 4 hours, 23 minutes.

"I escaped a very tough situation," Nadal said, "so it's a great thing."

At the end of the third set, Khachanov twice was two points from owning it and couldn't get across the line, helping Nadal with three double-faults in the tiebreaker. And while Nadal kept letting set points slip away, four in all, he made No. 5 count, and how. It was a quintessential Nadal point, too: a 40-stroke exchange — yes, 40! — that featured so much defense from Nadal until Khachanov netted a backhand, then tossed his racket on the sideline.

"I needed that set, of course," Nadal said.

The man he beat in last year's final at Flushing Meadows, No. 5 Kevin Anderson, got through his own tough test against an up-and-coming opponent, edging No. 28 Denis Shapovalov 3-6, 6-4, 6-4, 4-6, 6-4. 2016 U.S. Open champion Stan Wawrinka, who missed last year's tournament because of injury, lost to No. 25 seed Milos Raonic 7-6 (6), 6-4, 6-3. Raonic will face No. 11 seed John Isner in the fourth round.