Australian Open Round of 16 in quotes: Hsieh's wisdom, Sabalenka's regret, Swiatek's lesson

The Australian Open quarterfinals are set after an exciting weekend that saw 2019 champion Naomi Osaka save match points to defeat Garbiñe Muguruza, Serena Williams power past Aryna Sabalenka and Simona Halep end Iga Swiatek's Slam streak. Jennifer Brady and Jessica Pegula set up an All-American quarterfinal, Hsieh Su-Wei made major history and World No.1 Ash Barty cruised toward a stylish encounter with Karolina Muchova. 

Here's a collection of the best analysis, reflections and insight from the Round of 16.

Serena Williams knew all about Aryna Sabalenka's power game and she was ready to go toe-to-toe. 

"I don't know anyone that hit harder than Lindsay [Davenport], to be honest. She was the most power player I think I've ever played. So it was good. 

"It was definitely a lot of power. I think, if anything, it was definitely power, but I'm used to it in practice. I know how to get them. I was OK with it really. 

"If she wants to play power, let's go."

Garbiñe Muguruza could not make good on the two match points she had on Naomi Osaka in the fourth round, but she leaves Melbourne with a great perspective on the start of her season.

"It's a good start of the season. I feel like we're doing a good teamwork. I feel like when I go out there, I'm finding the way to do what we're working on, try to develop my game. It's a good start.

"You never know at the beginning how you're going to feel. There's years where you start and you feel like, OK, this year I didn't start that well. Other years, I'm playing good. So you never know.

"I'm happy with the tournaments that I played. Also the Australian swing, I played, I don't know, nine, 10 matches almost back-to-back. That was good. That was a good test for me physically, mentally. Just going on the court over and over, trying to have that high level. I'm pretty happy with my performances."

Every once in a while, Naomi Osaka needs to get out of her own head any way she can: 

"I felt the entire match I was overthinking. There was a moment when I got angry and hit my racquet on the ground. I feel like I released a lot of the thoughts that I had. It just made me go more into, like, instinct-based tennis.

"For me, I felt like Wim told me so much information before the match, it wasn't really clicking. But the closer it got, the more I felt like I could rely on that information."

Hsieh Su-Wei may be the queen of the funny one-liner, but she also offers great perspective on what her unorthodox career can teach others:

"I try to show people, the tennis is just not about the money, or you need to get a lot of money or sponsors. Even if you don't have any sponsor, you are doubles player, if you keep trying hard and working hard and find the way to get into the doubles or singles, doesn't matter, just try to keep playing. You still can go to somewhere you never dream, you never think about it. This is what happen, what I'm doing.

"I'm very happy that I made it, some good level. It can show a lot of people that anything can happen. Just keep working hard. Doesn't matter what happen. Stay positive and we will see."

"I quite enjoy to play every match, even if I get tortured. I think it's quite fun every time you play. I play Kvitova, never beat her. The one time I won a few more games, I say, Yes, today I win a few more games. She was laughing when we were shaking the hand.

"For me, I don't really care I win or I lose. I just try my best and play the game. All the girls, they play different games. Of course, there will be some difficult stuff on the court. It's very interesting when you have some difficult situation. I want to try to find a way and try to get into the game. 

"At least I try. If I lose, I don't lose anything. It's no problem for me."

Ashleigh Barty and Karolina Muchova will face off in the quarterfinals and they were both asked to recall their only previous meeting, a 6-3, 6-4 win for Barty at the 2018 US Open.

Barty: "I remember that match in New York, I remember coming off the court and saying to Tyz [Craig Tyzzer], I'm like, 'Karolina, she can play, she's a hell of a player.' At that time she was I think outside, maybe even 200 in the world.

"I'm not sure if she had injury layoffs, but I hadn't had much to do with her beforehand. Certainly that match in New York, it was a great match, a brilliant match. I remember we moved courts, we were playing at all hours of the night. One of those funny experiences where you look back on it now and just realize how special it was.

"I know that now we get another opportunity to do it in a quarterfinal of a Grand Slam. It will be a brilliant match. I know she's got the ability to maneuver the ball all around the court, play with variety, play with shape."

Muchova: "It was a nice game, I think. We play a bit similar, I would say. I remember that after the match she actually told me, like, to keep working, that I can make it to the top. So that was nice."

Aryna Sabalenka was kicking herself for how she finished her 6-4, 2-6, 6-4 loss to Serena Williams, which saw the 22-year-old climb back from 1-4 down in the third set before losing the final two games.

"I felt like I should win it and I felt I was doing really well, fighting really well. But the end of the third set, like, I lost two games in, I don't know, in a few minutes, like really quick. This is what I'm really disappointed with.

"I mean, I could lose this match maybe like 7-6 or whatever, but I have to serve better against these kind of players.

"I cannot just come back after 1-4 and just lose two games like 40-15? Like, come on. What was the reason for coming back in this match? You could just give this win to her? If you came back, then fight.

"OK, she took her serve. It's OK, this is what she usually does, this is nothing crazy with that. But then take your serve. You have to serve for you have to stay in the match. This is what I'm really disappointed with. 

"I would say that this is nothing to do with tennis. This is more in my head, like, why would I miss easy shots? I just served and then I think I made, like, unforced errors like four points, like easy points for her. Why would I do this?

"This is nothing about tennis, I would say. This is what I really disappointed with, because I'm still young, but I thought that I have enough experience to handle all this pressure."

Jennifer Brady's chilled out, positive mindset was a huge advantage as she entered hard quarantine before the Australian Open.

"I think pretty much everyone got through it. But a lot of people were complaining and I told myself I wasn't going to complain. I mean, there's way worse things going on in the world than me being stuck in a hotel room for 14 days. 

"Tennis Australia provided us with a bike. The last few days I had a treadmill. I had weights. I was able to train to work out. It was a small hotel room, but I was able to do everything that I needed to do to stay as fit as possible. 

"If I started feeling bad for myself or started complaining, I think it would have made the 14 days a lot harder than it was. There were a couple of us that were pretty positive and tried to each day just be like, 'OK, only five more days and, yeah, we're out.'"

Iga Swiatek got a tennis lesson from Simona Halep in her 3-6, 6-1, 6-4 loss, and it's one she hopes to learn from.  

"I'm pretty disappointed, because first set was kind of like perfect for me. Maybe it wasn't as perfect as French Open, but I felt that I'm playing good. 

"Of course Simona kind of changed her tactics, I think. And she even said that in an interview that she started playing with more topspin, and that's actually the thing that was hard for me to control my shots.

"Her shots were much more heavy than in the first set. I think I had to attack her much more times, because she was reaching everything. I wouldn't say that the second set was an example of that, because I made a lot of unforced errors at the beginning, and I felt that maybe it's better to already focus on the third. But in the third I give my all. Also, I was making more mistakes than in the first set, but obviously she was playing great.

"I think she just played really smart, and I have a lot of respect because it seems like she has a lot of options. And when something is not right for her, she just changes the tactics, and that's great. 

"But I think that's the difference between, like, the champions and less-experienced players, because I didn't feel like I had many options."

Serena Williams was asked about the depth of the WTA Tour: 

"I think it's been a lot of players that really could win the title since the beginning of the draw. I think there's so many players that can come out and have won Grand Slams and can keep winning. It's good. It's good to see. 

"It's good to see that I'm in that mix, too."