Sevastova, who retired from tennis in 2013 due to injuries before returning in 2015, almost let Stephens into the match in the second set as the American twice pulled back on serve at 2-1 and again at 4-3, but the fightback proved short-lived.
Pliskova, in 2016, had eliminated Williams in the US Open semi-finals - the 23-time Grand Slam victor is chasing her first major since becoming a mother past year.
Keys has beaten Osaka all three times they have played, including this year at the French Open and two years ago at the U.S. Open when she rallied from a 5-1 deficit in the third set.
"It means a lot but I was much more emotional for the quarters and now I feel like it's sort of business again", the 20-year-old said.
Projected to move as high as No.18, overtaking Venus Williams in the rankings (depending on results), and climb to No.11 by winning the title, Serena completed her 330th win in a Grand Slam and continued her bid to clinch her 24th major title and her 47th hard court title.
Tiger fails to break par in 2nd round of BMW
Northern Ireland's McIlroy briefly threatened to dislodge Woods before equalling the American's score. He also birdied 18. "I've got to make birdies", Woods said. "It helped a lot".
In the semi-finals, Williams will take on Latvia's world number 19, Anastasija Sevastova.
She's the only player remaining in the draw to have won a major title and remarkably she has now won 14 of her 15 Grand Slam matches since returning from giving birth to her first child. "I don't think I have another 10 years of opportunities to be able to play and win championships".
Sevastova retired in 2013, returned to the game in the same year and since then has played some of her best tennis in NY. Williams then cashed in a break point to level the set at 4-4 when Pliskova hit a backhand into the net. It's always a hard match, but I thought she played solid today. He's into the semifinals for the second year in a row, where he lost to top-ranked Rafael Nadal last year. The current World No. 26 Williams got off to a good start in the first set winning the first game, but an array of unenforced errors led to her being pegged back by the No. 8 seeded Czech in back-to-back games. It was Williams' first win over a top-10 player this season. But I got out of a tough second set and really found my feet and chose to be a little more aggressive. I'm just on my way on the tour and doing the best that I can.
"I'd been a couple of steps away at the last Grand Slam, so I'm definitely not ahead of myself", Williams said.
"Against Serena or Karolina, it's going to be a tough match - they play aggressive, they serve big", Sevastova said.
Barack Obama encourages people to vote: "This is not Coachella"
While speaking at the University of Illinois, Obama criticized what American politics have become, specifically targeting U.S. On Thursday, the former president is scheduled to campaign in Cleveland for Richard Cordray's campaign for Ohio Governor.
Pliskova broke back with Williams double faulting at 30-40 down.
Gauff's father, Corey, played basketball at Georgia State and her mother, Candi, ran track at Florida State.
Pliskova got another chance when Williams batted a forehand into the net, but another booming serve, a backhand victor and an unreturnable serve saw her safely through the danger.
"I love this game, and I love playing".
Mac Miller Dead at 26 After Drug Overdose
Known for songs like "Donald Trump" (2011), Miller has struggled with substance abuse and legal issues over the years. That's fine, that's good, that's life. "Pls (sic) take care of yourself", she wrote in a message to Mac .