She will play No 19 seed Anastasija Sevastova in the semi-final on Thursday, after winning her 14th consecutive quarter-final in a Major at the Arthur Ashe Stadium.
A year after missing the tournament and giving birth to her daughter during it, Williams reached the final in Flushing Meadows for the first time since 2014, when she won the last of her six U.S. Open titles.
While she gave up two straight games to Pliskova, and then narrowly dropped a third later on, Williams quickly finished her off to take the second set 6-3 and advance to the semis.
Williams is only playing her eighth tournament since becoming a mum, but had only dropped one set - in her last-16 match against Latvia's Kaia Kanepi - on her way to the last eight.
"I really feel like right now I'm playing free because I was having a baby this time previous year, so I have nothing to prove".
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We know we are not in Manchester United's league and it's a massive challenge for clubs like ours to get close to those guys." . Speaking to ManUtd.com , Mourinho said: "The pace with the ball and the organisation without the ball [was very good]".
It took five deuces for Williams to finally hold her serve, it was clear at this point that advantage was in the Czech's favour with Williams having to work a lot harder.
The 36-year-old American did not compete in NY a year ago, because she gave birth to her daughter during the tournament.
Sevastova, who retired in 2013 because of injuries and returned almost two years later, advanced to her first Slam semifinal.
"I want to just be able to get past the semis here", Williams said.
Earlier in the tournament, Williams made headlines when French Open officials warned they would not allow her to wear her Black Panther-inspired catsuit at the tournament next year. Tough loss a year ago.
Pliskova squandered three break point opportunities as Williams served herself to a comfortable 5-2, but the Czech star still had gas in the tank as she worked the 36-year-old around the court with some stunning winners at the net.
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At this level, at this stage of the tournament, Sevastova is going to have her work cut out for her.
"I still know that no matter whether I'm in the semi-finals or the finals, I have a really long way to go to win that".
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 negotiate the danger. "A year ago, I was fighting for, literally, my life at the hospital after I had the baby", Williams said, her voice wavering.
It was Williams' first win over a top-10 player as a mum.
"When you don't play big points well, the match can get away from you", she said. He committed back-to-back double faults to fall behind 4-1, and he eventually lost on another error.
Pliskova's game is built off her powerful serve. "I think today I didn't play those points well at all, even at the end, in the second set".
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Erdogan has warned against such a catastrophic outcome, and has much at stake in efforts to prevent it at the Tehran summit. The White House said that the USA would respond "swiftly and vigorously" if Syrian forces used chemical weapons in Idlib.
"She's a great player".
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