Angelique Kerber insists she is taking the U.S. Open on a match-by-match basis as she closes in on Serena Williams' No. 1 world ranking.
Williams must reach the final at Flushing Meadows to have a chance of retaining top spot and would need to win that match if Kerber were her opponent.
The German No. 2 seed produced a 7-5, 6-0 victory over 2015 Open finalist Roberta Vinci to reach the last four on Tuesday, but is not allowing herself to think beyond her next match, which will come against a rejuvenated Caroline Wozniacki.
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"I'm still trying to stay focused on match to match," Kerber said. "When I came here I was telling myself to just play round by round and play my best."
Kerber navigated a patchy first set, in which she came from a break down on three occasions, to claim what became a comfortable victory over Vinci.
"I think it is always difficult to play against Roberta. She is a great player and played so well last year here. She came out to play good tennis.
"I'm so happy to win it in two sets. To reach the semis here again means a lot to me."
Awaiting is Wozniacki, who powered into the final four with a crushing 6-0, 6-2 win over injured opponent Anastasija Sevastova in Tuesday's nightcap.
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The 26-year-old former world No. 1's quarterfinal triumph came in the wake of comments from her father, claiming retirement could be on the cards as she struggled with form and consistency in the last couple of years. But Wozniacki was tight-lipped regarding her future as her sudden resurgence seems to be breathing new life into her once-dominant game.
"I think I don't want to really talk about that now," Wozniacki told reporters after being quizzed about her dad's comments. "When I feel ready to open up and say something then I will, but for now I'm just here to play this tournament.
"Hopefully I have two more matches here. It's really all I'm focused on right now."
Wozniacki, a two-time runner-up at Flushing Meadows, is into the U.S. Open semifinals for a fifth time.
Kerber leads their head-to-head history 7-5, but Wozniacki holds the upper hand on hard courts, winning five of their nine such meetings.
"I think the fact that I have friends and family here and I can just go home and relax and kind of unwind, it's really helped me to kind of just enjoy it and not look ahead and not stress and just show up," Wozniacki said. "I'm like, Well, I get another day; I get another chance. It's great."
Omnisport's Sacha Pisani contributed to this report.