The data says winning a junior grand slam doesn't mean you'll be a star

After a long wait, tennis seems to finally be embracing a trend towards youth. The era of Rafael Nadal and Roger Federer has passed, with Novak Djokovic remaining the last bastion of the "Big Three." Meanwhile, the women's tennis era led by the Williams sisters has also given way to a new generation of star players.

After years of veterans dominating the sport, the tide seems to be gradually turning towards the younger generation. At this year's Australian Open, many young players defeated more favored opponents. This is the first time since the 2006 French Open that three teenagers have defeated top-ten ranked players in the same Grand Slam event, with João Fonseca, Mirra Andreeva, and Jakub Mensik all showing great potential.

On the women's side, Mirra Andreeva continued her excellent performance from the past 12 months, with the 17-year-old reaching the round of 16. Australian fans also turned their attention to the future this tennis summer. Emerson Jones, 16 years old and the world's top-ranked junior, is still competing for the women's singles title. Jones is the first Australian player to be ranked number one in the junior rankings at the end of the year since Jelena Dokic in 1998. Experts have already predicted a bright future for Jones.

Cruz Hewitt, the son of former Australian world number one Lleyton Hewitt, also received widespread media attention this summer, participating in the men's and junior events at the Australian Open. Although he was eliminated early in both events, he has won several junior titles in the past 12 months. Despite the rise of young stars, it is not always the top-ranked junior players who dominate in the future.

Djokovic, Nadal, and Federer combined have only won one junior Grand Slam title—Federer's victory at Wimbledon in 1998. The three most successful women's singles players—Serena Williams, Steffi Graf, and Margaret Court—failed to win any junior Grand Slam titles. So, to what extent does junior performance translate into adult success? It turns out to be a bit complicated.

For most people, the easiest way to track emerging talent is at Grand Slam events. While the main courts are occupied by today's stars, the outer courts are filled with players who hold promise for the future. These young players are often teenagers, frequently playing in front of sparse crowds. Those who stop to watch may get a preview of the sport's future. But this may not necessarily be the future Australian Open champions.

The last player to win a junior Australian Open title and eventually win the adult title was Victoria Azarenka. The Belarusian player won the girls' junior singles title in 2005 and went on to win the women's adult title in 2012. On the men's side, the wait was much longer. Stefan Edberg won the boys' junior singles title way back in 1983 and won the men's adult title in 1987. Since 1984, only 5 of the 183 boys' junior Grand Slam champions have eventually won an adult Grand Slam title.

In women's tennis, junior Grand Slam success is more likely to translate into adult achievement. Since 1984, 13 of the 133 junior Grand Slam champions have eventually won an adult Grand Slam title. In 2018, both Coco Gauff and Iga Świątek won junior titles. Since then, both have established themselves as top players on the WTA Tour. However, winning a Grand Slam title is not the only measure of success. There are only a few Grand Slam events each year, and the crucial moments often determine the champions.

Looking at the current composition of the world's top 20 players, the situation is slightly different. Among the top 10 men in the world, 4 have won junior Grand Slam titles, and among those ranked 11 to 20, another 3 have won junior Grand Slam titles. On the women's side, 4 of the current top 10 players have won junior Grand Slam titles. Some junior Grand Slam champions struggle to adapt to the speed and power of top-level tennis. For every Gauff or Federer, there are two or three players who struggle for years in lower-level events.

A more comprehensive look at the performance of junior players can provide a better understanding of how they will adapt in the future. Similar to the ATP and WTA tours, the ITF (International Tennis Federation) has established junior rankings for players participating in Grand Slam events and other prestigious junior tournaments around the world. The list of year-end junior number ones includes names like Roger Federer, Ivan Lendl, Martina Hingis, and Victoria Azarenka. Some have carried their junior success into the adult ranks, but many have not.

Analysis by ABC Sport shows that only about one-third of elite junior male players, and just under half of elite junior female players, eventually break into the world's top 100. The top 100 is an important historical threshold, representing that a player can make a living from tennis. Those ranked slightly higher in the junior rankings also have higher expectations for the future. This suggests that quality often shows early, especially in women's tennis.

But what about those who didn't reach the top of the junior rankings? Where did they come from and how did they reach the top? Unsurprisingly, junior tennis does not have the same wealth and rewards as the adult tour. For many players, the junior tour is an expensive activity that takes young people away from school and support networks to pursue a difficult goal. As a result, many young players (and their families) are looking for the best and fastest way to transition to the main tour.

Take Cruz's famous father, Lleyton, for example. Lleyton Hewitt was the youngest player in the Open Era to reach world number one, at just 20 years old. The South Australian announced his arrival to the world by winning the Adelaide International in 1998 at the age of just 16. That instant success quickly ended his junior career. The elder Hewitt never made it to the quarterfinals of a junior Grand Slam in five attempts. His highest junior ranking was a relatively low 17th.

This is similar to the story of Rafael Nadal, who was always considered a Spanish prodigy. Nadal only played in one junior Grand Slam event, the 2002 Wimbledon Championships, where he reached the semi-finals at the age of 16. Although Nadal led Spain to win the Junior Davis Cup, he quickly transitioned to the Challenger level—one level below the main tour. Nadal also missed important junior events in order to complete his education. In total, Nadal's highest junior ranking was 145th in the world, greatly underestimating his abilities.

These stories are not uncommon. In the past, junior players would try to move up as soon as they showed enough power and stamina. The data related to junior rankings also confirms this. Generally speaking, young players in the top 40 of the year-end junior rankings are more likely to become successful adult professionals. Those who stay until their 18-year-old season are less likely to reach the top of the adult rankings. This is true for both the men's and women's tours. Younger junior Grand Slam champions, like former world number one Hingis, more often carry their success into the adult ranks.

Hingis won her first junior Grand Slam title at the age of just 12. The Swiss star won her first doubles Grand Slam title at 15 and her first singles Grand Slam title at 16, reaching the pinnacle of the tennis world. Hingis may represent an extreme case, but she is an example of a young player entering the professional circuit. Historically, players have tried to jump into the adult ranks as early as possible to try and make a living from the sport.

But this may be changing. In recent years, major tennis organizations have been working to improve these development pathways. As tennis continues to grow globally, it is becoming increasingly difficult to reach the top of the sport. Therefore, global tennis governing bodies have been working to find the best ways to support junior players in their transition to the adult game. The WTA and ATP have gradually increased incentives for highly ranked junior players, including providing special entry rights to some events for top juniors and junior Grand Slam champions.

These special entry spots have helped former top-ranked junior players like Fonseca to develop their game at an appropriate pace, while still progressing towards the adult ranks. This may also allow more junior players to stay in the junior ranks for a little longer, so that when the time is right, their eventual journey to the top is easier. The next generation will be here soon. That is, of course, unless veterans like Djokovic stop them first.