Naomi Osaka was impressed with the way Marta Kostyuk played against her at the US Open. When asked what she thought of her opponent she simply said:

"I'm kind of scared of good she's going to be in the future."

And while that is an enticing thing to think about, Kostyuk already proved she is good by making Osaka go the full distance. Some of that fault lies with Osaka as she herself admitted after the match:

"I was very displeased with how I was performing towards the end of the second set. The thing that made me most displeased was probably the decisions that I was making and the fact that I started becoming way too passive and hoping that she would make an unforced error. For me, I felt everything was going really well for her during the tiebreak. And I remember she came to the net, and I hit it as hard as I could towards her, and she made it, and for me I was just, like, Whoa, this is unbelievable."

One game in the 3rd set was key and Osaka herself highlighted it as the crucial game according to her. She said:

"I feel like that game was very important. Honestly, I'm not sure how it would have gone if she won it and I would have had to break her back, but thankfully I don't have to think about it too much."

https://twitter.com/usopen/status/1301954890609164288