US Open 2021: Who is most impressive - Leylah Fernandez, Emma Raducanu or Carlos Alcaraz?

Leylah Fernandez defeats Elina Svitolina in three sets (0:42)

Leylah Fernandez advances to the US Open semifinals after defeating Elina Svitolina in three sets. (0:42)

A US Open without Venus and Serena Williams, Roger Federer and Rafael Nadal surely won't live up to Slam standards for tennis fans, right?

Wrong. The upstart teenagers have taken Flushing Meadows by storm on the men's and women's sides, advancing through the brackets and upsetting favorites along the way, as if they own the joint.

Our experts offer their thoughts on the up-and-comers, if we can still call them that.

Which of the breakthrough youngsters has impressed you most this fortnight?

Bill Connelly: She hasn't played the stiffest competition, but Emma Raducanu. She has won three qualifying matches and four main-draw matches, and not only has she not dropped a set yet, she's been taken to even 6-4 in only three of 14 sets. She dominates on her serve, she hits a low number of unforced errors for how high her winner total is, she's been unbelievable.

Aishwarya Kumar: Leylah Fernandez. What an incredible fighter. First Naomi Osaka, then Angelique Kerber. Right after, Elina Svitolina. Two former world No. 1s. Two Grand Slam champions. Two top-5 players. Fernandez is the youngest to make the US Open semifinals since Maria Sharapova in 2005 and is the first player to beat two top-5 players in the same major since Serena Williams in 1999.

Her crosscourt forehand is lethal. Her backhand is fantastic. And her serve literally stops the best players in their tracks. She is 19 and already is one of the most well-rounded players in the tournament. The story writes itself.

D'Arcy Maine: This is definitely one of those questions where there truly are no wrong answers. Fernandez and Carlos Alcaraz have recorded the bigger wins against tougher opponents, but Raducanu came through qualifying and has backed up what she did at Wimbledon with this seven-match run. Her fourth-round appearance at the All England Club put her on the map, but this event has launched her into the stratosphere and proved she's no fluke. And to do that in the first two majors of her career? It's hard to get much more impressive than that.

Ohm Youngmisuk: Fernandez without a doubt. It is one thing to stun Osaka and perhaps catch her on a bad day in what has been a rough season. But Fernandez continues to back up each win with even more fight and show she's no fluke. Nothing has been given to her. After taking out Osaka, she stood toe-to-toe with Kerber and then outlasted Svitolina in a third-set tiebreaker. Each time Fernandez is tested and could wilt under pressure, the kid responds. She has serious moxie and is already on one of the all-time special US Open runs.

Whose run has been most unexpected?

Connelly: Fernandez. She has won five matches over the last week and a half after having won just four since the French Open. To not only find her form at the perfect time but also find out that that form is capable of beating Osaka, Kerber and Svitolina back-to-back-to-back? That's incredible. She plays an aggressive and exciting game, and if things click for her from this point forward, it wouldn't be all that much of a surprise, but wow, was this unexpected.

Kumar: Alcaraz. I knew he was talented, but I didn't expect him to step up the way he did in this tournament. Against Stefanos Tsitsipas, he looked flawless, his forehand stunning the No. 3 seed. After playing a five-setter against Tsitsipas, he comes back and wins another five-setter against unseeded German Peter Gojowczyk.

Maine: Very little on the women's side surprises me at this point, and we've seen a number of unseeded teenagers come from seemingly nowhere into the second week of a Slam before (see: Gauff, Coco) so I'm most surprised by what Alcaraz has done. The adjustment from playing best-of-three (in juniors) to best-of-five can't be understated, and so many younger male players struggle with that early in their major careers -- but not Alcaraz.

Sunday was just the third five-set match of his career, but he has looked like a veteran in both of the matches that have gone the distance in New York. There has been no question about his potential over the past two years, but to see him achieve this level of success so fast is remarkable.

Youngmisuk: The ATP Tour has known about Alcaraz's potential, but now the world is getting to know him. His fifth-set tiebreak win over Tsitsipas is probably going to still go down as the match of the tournament. The poise, quality and electric game he showed in that fifth set looked like the kind of stuff that could lead to major wins in the near future.

Whose overall trajectory has surprised you the most?

Connelly: Jenson Brooksby's trajectory has changed dramatically in the past four months. A burgeoning heavyweight on the challenger tour, he had to eke out a couple of three-setters just to reach the French Open field, where he lost to Aslan Karatsev. But then he reached the finals in Newport and the semis in Washington to jump into the top 100. And then he beat Karatsev (and Taylor Fritz) and took a 6-1 set from Novak Djokovic! He's learning and adapting at an incredible rate.

Maine: Raducanu. Before Wimbledon -- just over two months ago -- she was playing almost exclusively ITF events and ranked No. 338 in the world. Now, she's here in the quarterfinals, and following Monday's win, she's projected to reach No. 74. A win Wednesday would put her just outside the top 50. While it's not like Fernandez and Alcaraz have been on the tour for that much longer, they both have been playing WTA- and ATP-level events for nearly two seasons. What Raducanu has been able to do with her limited tour opportunities has been incredible.

Kumar: Raducanu. Her overall ascension has been the most surprising storyline at this year's US Open. A month after she made her WTA Tour main-draw debut, she made the round of 16 at Wimbledon, her first Grand Slam, and became the youngest British woman in the Open era to do so. Then she had to play the qualifiers to get to the main draw of the US Open. She has played seven matches heading into the quarterfinals, but somehow looks fresher and more confident with every match. The draw has favored her, but she has dominated every match, losing just 15 games in the entire tournament. That's a remarkable achievement considering she started the year ranked No. 338.

Youngmisuk: Even Raducanu is surprised by her run, but perhaps she shouldn't be. After all, she became the youngest British woman in the Open era to make the round of 16 at Wimbledon before retiring because of a breathing difficulties. Raducanu's future appears bright and on the rise.

Which of them do you believe will have the best career?

Connelly: This is where recent events can cloud our judgments. All of these youngsters -- Fernandez, Raducanu, Alcaraz, Brooksby, etc. -- have looked fantastic over the past week or so, and if any of them maintain this form, they're in for a lovely career. But while Raducanu's Wimbledon and US Open runs have been utterly dominant and loaded with upside, they have come entirely against unseeded players. The upside Alcaraz showed in beating Tsitsipas, and the fortitude he showed in fighting a big-win hangover to beat Gojowczyk in the next round, told me a lot. So do his movement and all-court game. By a nose, he's my pick.

Kumar: Fernandez. She's going to be a multitime Grand Slam champion.

Maine: It's honestly impossible to make this kind of prediction now, but I don't think it would be surprising to see all three of these teenagers win a major someday. Heck, at this rate, maybe one will do it this weekend. They all have the potential to be top 10, if not better, and be serious contenders for titles over the next decade-plus. The talent and poise is unquestionably there for all three, but I think it will come down to who is able to deal best with the pressure and the expectations. We've seen others struggle with that after early success, so in part it comes down to who has the best team around them helping them adjust to their newfound fame.

Youngmisuk: Before retiring, Alcaraz showed the kind of stuff that could be next-level star talent. While Djokovic isn't going anywhere and Nadal and Federer are on the mend, Alcaraz might be getting the kind of jump start needed for a youngster like himself from this Open. The experience and confidence he gainrf here is invaluable, and he certainly has top-10 weapons in his game.