But Osaka didn't crack a smile.
Williams, considered one of the all-time greats in tennis, has a fan in Osaka, who considers the historic final her "dream match", according to TIME.
Osaka, who is the first Japanese woman to reach the final of a Grand Slam, had to fight harder than the score suggested to get past 14th seed Keys, who paid the price for a lack of killer instinct.
"I'm just going to go out there and play". She has all the raw tools necessary to win this match, and she's been the best player in the tournament thus far.
As in her semi-final win over Karolina Pliskova, Williams took a while to warm up, dropping her serve in the opening game.
After yet another show of force at the U.S. Open, Serena Williams is one match away from reaching yet another milestone in an already incredible career. "Even in good matches, I still [see] what was negative and what was wrong", she said. But Osaka struggled from there.
The nerves surfaced when the Japanese found herself trailing 0-40 in her second service game, but she managed to keep it together, battling back to deuce and saving another break point to hold and level the opener at 2-2. She was handed early exits at the Citi Open, the Rogers Cup and Cincinnati.
"To come from where I was then, in the hospital bed, not being able to move and walk and do anything, now only a year later I'm not just training but I'm actually in these finals, in two in a row".
Naomi Osaka stands in way of her idol Serena Williams
Safe to say, those losses feel like a lifetime ago. She told the US Open, "I used to play here when I was a little kid, so these courts aren't new to me. She was very impressive". What I really love about Naomi is that she really preserved that innocence somehow. It will be a really good match. I had one more to go still.
She's not alone in her complimentary words.
Like Williams, Osaka has a tennis-playing sister, Mari. And in last year's U.S. Open, she defeated defending champion Angelique Kerber in the first round. If not the present.
The Japanese youngster broke into tears of joy following that win over Sabalenka but remained calm after her victory in the semi-final.
In August, when she felt like she was losing the drive to play tennis, she hired four-time Grand Slam doubles champion Rennae Stubbs as her new coach. She had four operations following the birth of her daughter, Olympia, during the Open because of complications related to blood clots. Two years later, and still just as revered for her nerdy coolness, it seems as if she might be on her way. She shouldn't be afraid to get into longer rallies - that's where she can use her youth to her advantage - but she also shouldn't cower at the thought of making aggressive plays to end points quickly with her booming forehand.
She is the oldest U.S. Open finalist of all time, besting then-34-year-old Martina Navratilova's record in 1991. Osaka hits a brutal ball and has been a revelation this event, but she's essentially mini-Serena. With the 2020 Olympics in Tokyo, it feels as if she would only become more desirable to companies as one of the host country's top athletes.
Follow along with Saturday's final with our live updates. When asked if she had any message to relay to her upcoming opponent, she giggled, "I love you". "You're just asking me. I don't dream to lose, so".
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