This 2021 US Open has been a revelation when it comes to 18-year-olds.

Three of them reached the fourth round of the season’s last Grand Slam – Leylah Fernandez, Emma Raducanu and, on the men’s side, Carlos Alcaraz.

“Seeing all these teenagers, the youngsters doing so great at the US Open and the other tournaments, too, is also eye-opening I think to the world,” Fernandez said Sunday. “Because there is not only like one group of tennis players, but there is a new wave of young generations that’s coming up, and just trying to make an impact in the tennis game as much as they can.”

Impact? These teenagers have dramatically changed the landscape of what elite tennis might look like going forward. Two of them, Fernandez and Alcaraz, are already into the quarterfinals. Credit Fernandez, who turned 19 on Monday, with doing a lot of the heavy lifting.

Ranked No.73, she knocked out No.3 seed — and four-time major champion – Naomi Osaka in the third round, then mastered three-time Grand Slam winner Angelique Kerber 4-6, 7-6 (5), 6-2 in the fourth.

When reporters asked the Canadian Fernandez what had surprised her most during this run, she responded candidly.

“I have been working hard every day since the day I started playing tennis and since the day I set my mind to being a professional,” she said. “I expected that one day my tennis game is going to come through and that I’m going to be on the big stage in front of a big crowd playing against big players and also getting the wins.

“I’m not surprised of anything that’s happening right now.”

Kerber, 33, was impressed.

“Of course when you reach your first quarterfinals in a Grand Slam, it’s always a lot of emotions,” she said of Fernandez. “She had nothing to lose today, and I think she’s enjoying her tennis.

“I think, yeah, that it’s just a start of a great career.”

Fernandez will be tested again Tuesday in her quarterfinal match against Elina Svitolina. The other one features No.2 seed Aryna Sabalenka against No. 8 Barbora Krejcikova, two of the year’s most consistent players.

A closer look at the two singles matches on the schedule:

No.5 Elina Svitolina vs. Leylah Fernandez

When Svitolina went 0-2 in the two big US Open precursors in Montreal and Cincinnati (losing to Johanna Konta and Angelique Kerber), she went to Plan B.

Her coach, Andrew Bettles, thought she needed some matches, so Svitolina accepted a wildcard into the Chicago 250 event.

“For sure it was a good decision, good call from Andy,” Svitolina said Sunday. “I had some good matches because obviously after Cincinnati, that match against Angie, was maybe not my best performance.”

The 26-year-old from Ukraine dropped her first set in Chicago, to Clara Burel but went on to win all five matches. Add in four more in New York – including an impressive 6-3, 6-3 fourth-round victory over Simona Halep – and Svitolina has won nine straight. She has yet to drop a set at the Billie Jean King National Tennis Center.

“Right now I just want to focus on this moment where I’m feeling good,” Svitolina said. “I just want to build on that, I want to focus on the next challenge that I’m going to get in the next round.”

That would be Fernandez, who seems to be enjoying this whole thing. In the crucible of the third set against Kerber, she actually smiled – more than a few times.

“I think from a very young age I’m just a happy-go-lucky girl,” Fernandez said. “I never really take things too seriously or some things too hard. During the past year with all the difficulties around the world, I was lucky enough to have my family, my sisters, they were amazing and super supportive. Every time I’m feeling down, they were always there to bring me back up.

“I think sometimes the way that my parents would teach me off court, saying that you can’t take things too seriously, you’ve got to be mature but at the same time just be a kid, let loose, have fun, eat chocolate when you want to, and just have fun, watch movies, go past your bedtime.”

READ: Leylah Fernandez on beating Osaka, self-belief and the power of family

For the record, this is Svitolina’s eighth quarterfinal appearance in a Grand Slam singles event, compared to just one for Fernandez. The last time Svitolina played this event, two years ago, she reached the semifinals before losing to Serena Williams.

“Right now, I’m feeling good,” Svitolina said. “I think I’m playing really aggressive right now. I think the most aggressive I’ve ever been, making lots of winners, serving really good. I want to keep this going, feeling that I'm in a good mind.”

Head-to-head: 1-0, Svitolina (2020 Monterrey quarterfinal, 6-4, 7-5).

No.2 Aryna Sabalenka vs. No.8 Barbora Krejcikova

If victories are everything in this bottom-line sport, this matchup will tell us a lot.

Both athletes have collected 41 match-wins so far this year, and the winner will draw even with Ashleigh Barty for the year’s best total.

In the fourth round, Sabalenka forcefully defeated No.15 Elise Mertens 6-4, 6-1, while Krejcikova was a 6-3, 7-6 (4) winner over No.9 Garbine Muguruza.

For Sabalenka, a 23-year-old from Belarus, it confirmed her new place in the tennis hierarchy. Before this year’s Wimbledon, she had failed to advance to a Grand Slam quarterfinals in 14 attempts. Now, she’s done it back-to-back.

“I don’t want to say 'expect this,' because, I mean, you never know,” she said after beating Mertens, her sometimes doubles partner. “I’m just really happy to be in the quarterfinals here because I really like playing at the US Open, especially with the crowd and the atmosphere is really enjoyable here.

“At the Wimbledon, it was my first time in the quarterfinals, so it was kind of something new. It’s still something new for me, because at the US Open it’s the first time, but it’s already second time, so the second time feels a little bit different.”

Krejcikova’s been playing so well, it’s difficult to remember that it’s her very first US Open. Her measured takedown of Muguruza demonstrated the kind of player she’s so quickly become. After beating three players ranked outside the Top 100, including two qualifiers, this was a two-time Grand Slam champion. And to think, a year ago the 25-year-old from the Czech Republic had played in only three major singles draws. Her breakthrough came at this year’s French Open, doing something that Sabalenka has yet to do.

“I’m really happy with the consistency I’m showing right now in the Grand Slams,” Sabalenka said. “Hopefully I can go win one.”

Head-to-head: 1-0, Sabalenka. They have met three times in doubles, including this year’s Australian Open, when Sabalenka and Mertens won in straight sets over Krejcikova and Katerina Siniakova. Their only singles match occurred in the 2020 Linz semifinal, with Sabalenka prevailing in three sets.