In a high-quality affair on Wednesday involving only one service break in each set, the 29-year-old Keys held sway when it mattered most, setting up a semi-final with either Polish world No.2 seed Iga Swiatek or US eighth seed Emma Navarro.
"I felt like I had to start playing a little bit more aggressively and try to get to the net a bit quicker," the 19th-seeded Keys said in her on-court interview.
"She was controlling a lot of the points and making me run so I felt like I needed to try and get on the advantage a little bit quicker and luckily I was able to do that."
Elina Svitolina came up just short against Madison Keys. (James Ross/AAP PHOTOS)
Keys' best result at a major was reaching the final of the 2017 US Open, while she also reached the last four at Melbourne Park in 2015 and 2022.
"I think I play a little bit smarter for sure," said Keys, when asked to compare the difference between 2015 and 2025.
"Probably a little bit less fearless.
"But to be here 10 years later in the semi-finals again, I'm really proud of myself."
No.28 seed Svitolina claimed the only break of the opening set in the eighth game and then closed it out 6-3.
The 30-year-old Ukrainian was made to work hard by Keys in her opening two service games of the second set but managed to hold both of them, including with a brilliant instinctive volley winner in the fourth game that appeared to shock both players.
But Keys would not be denied in the sixth game, finally claiming her first service break of the match at the seventh attempt to go up 4-2.
Minutes later the match was tied up at one set apiece.
Keys finally got her nose in front by claiming the only break of the final set in the fifth game before closing out the match in one hour and 53 minutes.
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