Serena Williams revealed she had watched plenty of Karolina Pliskova since her loss to the Czech at the 2016 US Open.
Williams battled past Kaia Kanepi 6-0 4-6 6-3 on Arthur Ashe Stadium on Sunday to reach the quarter-finals at Flushing Meadows.
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The American's last loss in New York came in 2016, when she was beaten by Pliskova in the semis.
Ahead of another meeting with the Czech, Williams said she expected a different encounter.
"She came out strong and she came out very well. I have watched her a great deal since then," she told a news conference.
"I have taken a lot from that match and I think we are in different positions now. It will be an interesting match."
Pliskova has been in fine form at the year's final major, moving into the last eight without dropping a set.
Williams pinpointed the 26-year-old's serve as the best area of her game and said there were few weaknesses.
"Obviously her serve. She has a really good forehand. In fact, she doesn't do a lot of things bad," she said.
"Obviously I think she was number one last year, so she got there for a reason. She has a lot of strong parts to her game."
