After defeating two-time Australian Open champion Victoria Azarenka to reach the quarterfinals, Barbora Krejcikova wore a look of disbelief.

“I wouldn’t say it’s disbelief,” she told reporters later. “I would say it’s just something special and magical. Couple months ago I wasn’t even Top 100. Now I’m here and I’m playing on the biggest stadiums with the champions.

“I’m actually able to beat them.”

Madison Keys, who meets Krejcikova in a quarterfinal Tuesday, won a total of 11 matches last year. A win over the reigning French Open champion would give her 11 – in January.

Australian Open: Scores | Draw | Order of play

“I was just at a very high anxiety level all of the time,” Keys said of 2021. “I wasn’t sleeping as well. It just felt like there was literally a weight on my chest just because I became so focused and obsessed with it that I wasn’t enjoying really anything because it’s all that I was thinking about.

“I think just my [new] mindset really let me play that good tennis. That’s really what I’ve been trying to focus on, just giving myself the opportunity to allow myself to play tennis like I did today.”

World No.1 Ashleigh Barty and No.21 seed Jessica Pegula, who meet in the other quarterfinal from the draw’s top half, are playing that kind of tennis, too. Here’s a deeper dive into both matches:

No.1 Ashleigh Barty versus No.21 Jessica Pegula

The streak is over. Long live the streak.

When Amanda Anisimova broke Barty in the second game of the second set in their fourth-round match, it ended an astounding run of 63 consecutive service holds, going back to her title in Adelaide.

“Yeah, it didn’t bother me too much,” said the even-keel Barty. “Honestly, I’m not counting how many games I hold in a row or not. The fact I was able to reset, break straight back, was really important, just to be able to reset myself, go again and continue to do the right things.”

Barty’s been doing that a lot lately. She broke the resurgent Anisimova three times in that second set and went on to win 6-4, 6-3. Barty has dropped only 15 games in eight sets.

After a terrific 2021 season, Pegula had a rough start to 2022. She lost her first two matches, in Melbourne and Sydney, and was extended in the first round by Anhelina Kalinina. The score was 4-6, 7-6 (1), 7-5 and went 2 hours, 53 minutes.

But now, after defeating No.5 Maria Sakkari 7-6 (0), 6-3, the American’s right back where she was a year ago. Barty and Pegula have met only once, at 2019 Roland Garros, when Barty took her first step to a first major title. They have practiced, too, which gives Barty a good knowledge of Pegula’s unique strokes.

“It’s a bit different because she’s able to hold baseline really well,” Barty said. “Her swings are quite linear and she gets a racquet behind the ball and swings through the path. The ball comes at you at a different trajectory, and her ability to absorb pace and then add to it when she wants to is exceptional.”

Pegula now has eight career wins over Top 10 players, and all of them have come since the start of last year. That success has a downside, too.

“I did really well last year, which is great,” Pegula said. “I wish I didn’t because now it’s like every tournament there’s points or something coming off. I think winning that first round really helped me. I really had to dig deep.

“It’s a long year. I’m excited I did well here and hopefully I can take that into the rest of the year like I did last year.”

Head-to-head: 1-0, Barty, first round 2019 Roland Garros.

No.4 Barbora Krejcikova versus Madison Keys

Before last year, Krejcikova’s best Grand Slam singles efforts were the fourth round at Roland Garros and the second here in Melbourne. She hadn’t even qualified for the main draws at Wimbledon and the US Open.

One month into 2022, the Krejcikova is a quarterfinalist at the Australian Open and her resume includes a French Open title, a fourth round at Wimbledon and a US Open quarterfinal.

“Yeah, I mean, it’s amazing that I can say that I’m a quarterfinalist right now,” Krejcikova said after beating Azarenka 6-2, 6-2. “I would just say it's like a very nice surprise. Not surprise. I don’t know the English word. Yeah, I think it’s just really, like, amazing and special feeling that I go there and I want to win and I’m actually able to win against her.”

Keys, who was ranked No.87 to begin the year, could say the same. She’s into her first major quarterfinal since 2019 Roland Garros. After taking out the No.8-seeded Paula Badosa 6-3, 6-1, she talked about her mindset makeover.

“My biggest mindset change is just trying to enjoy tennis, take some of that just internal pressure that I was putting on myself,” Keys said. “It was honestly freezing me. I felt like I couldn’t play at all.

“Just taking that away and putting tennis into perspective. That it’s a sport, something that when I was little I enjoyed doing and loved doing it. I was letting it become this dark cloud over me. Just trying to push all of that away and leave that behind last year and start fresh this year.”

Pegula is thrilled to see Keys smiling again.

“You’ll have some rough patches but always keep your goals there, keep your head up, not get too down on yourself,” Pegula said. “You can see how it can kind of spiral. Is been really cool just to see her happy out there competing.

Keys’ big serve (75 aces in 11 matches this year) and crushing forehand are back.

“Tennis can change in a week,” Keys said. “Just knowing that it will eventually get better, you just kind of have to hold on to that. Obviously when you’re in week four, five and six of not good results, it gets a little bit frustrating.

“Just knowing that you can get yourself out of it and it can switch very quickly, I think you just have to keep reminding yourself of that.”

Head-to-head: 0-0.