Svitolina retired down a set and a break in a 2015 match at New Haven, and then they met in fourth round at the 2017 US Open, with Keys pulling out the 7-6 (2), 1-6, 6-4 win.
Despite looking down and out, Osaka turned around a set and 1-4 deficit to win in three, 5-7, 6-4, 6-1, to move to the fourth round of the Australian Open.
The 2018 US Open champion, targeting back-to-back Grand Slam victories, now trails Svitolina 3-2 in their head to head, having lost both hard-court encounters against the Ukrainian in straight sets a year ago in Dubai and Miami.
If the quarterfinal match goes in her favour, Osaka is likely to face Serena Williams, whom she beat in the final of the 2018 US Open to clinch the title. So Dayana Yastremska, an 18-year-old from Ukraine, found herself wiping away tears as she walked to the net.
"I had to put my level up, I'm glad I handled the pressure", said Svitolina, who scored her biggest career win at the WTA Finals in Singapore last October.
Like her opponent, this match is set to be the first major test for Naomi Osaka who will also be confident about her chances of winning.
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Osaka had more to be upset about in the second set, falling 3-0 and 4-1 behind, but she suddenly clicked into gear and won five successive games to avoid elimination and 10 of the next 11 to earn a showdown with either Anastasija Sevastova or Wang Qiang. I just had to stay very strong.
"It was very hard because the sun was burning my eyes when I was tossing the ball". Japan's Naomi Osaka reacts during her match against Latvia's Anastasija Sevastova. The reward for the 27-year-old French Open champion is probably the toughest challenge in the women's draw at Melbourne Park, a fourth-round date with the younger Williams sister, Serena.
Trailing 3-0, Elina fought back to win five straight games, only to lose serve at 5-4 while serving for the match, adding more fuel to already very dramatic encounter.
"I walked into the match knowing that she was going to do a lot of unusual things, no offense", Osaka said. The victory helped him become the first player from Greece to reach the quarter-finals at a major.
That she does. She also makes abundantly clear just how much every point means to her. "I think she's a good talent". In the end, Svitolina managed to avoid the match tie break, sealing the deal with the crucial break in game 12 that pushed her over the top.