Nicolai Budkov Kjaer
It's fairly rare to see young talents coming out of Scandinavia who could potentially make a splash, but the 19-year-old Norwegian Nicolai Budkov Kjaer could be an exception to that rule.
Budkov Kjaer, the 2024 Wimbledon boys' champion, quietly assembled no less than four titles on the Challenger Tour this season after winning in Glasgow, Tampere, Astana, and Mouilleron le Captif to boost his ranking from outside the Top 300 at the start of the year to a career-high No. 136.
Kjaer, who is managed by his father, Alexander Kjaer - the former CEO of the Norwegian Tennis Federation - has plenty of weapons in his arsenal to suggest that he could move up into the top 50 in the world during the next season and perhaps even have potential for the top 10 in the years to come.
Jannik Sinner's coach, Darren Cahill, describes his forehand as a 'hammer', and at 6'3", Budkov Kjaer is capable of generating lots of pace with his serve. He needs to add more consistency to his backhand, but mentally, he has already demonstrated plenty of coolness to close out matches at crucial moments.
Dino Prizmic
While Novak Djokovic is surely approaching the end of his career, the next Balkan tennis star in the making is waiting in the wings to make an impact on the ATP Tour.
Dino Prizmic already tested himself against the Serbian legend in the first round of last year's Australian Open when he pushed Djokovic to the limit in a four-hour, first-round battle. Afterwards, Djokovic praised the youngster, saying: "It was like playing myself in the mirror."
The 20-year-old boasts an impressive 31-13 record across all levels in 2025, which has propelled his ranking from outside the Top 200 to a career-high No. 115, mainly thanks to a huge number of impressive performances on clay.
Prizmic, who won two ATP Challenger Tour titles in 2025, enjoyed a 14-match winning streak, suggesting that he will soon be a household name at ATP level.
The Croatian needs more ATP experience, but that chance may also be waiting right around the corner with the 2023 Roland Garros junior champion playing aggressive baseline tennis, dictating rallies with heavy topspin, and showing a remarkable tennis IQ.
Justin Engel
18-year-old Justin Engel has received the perfect launch pad for making a breakthrough in 2026 after he was called in to replace Jakub Mensik at the Next Gen ATP Finals in Jeddah to possibly follow in the footsteps of Jannik Sinner and Carlos Alcaraz when they were the same age.
This year, he became the second-youngest player (behind Rafael Nadal) since 1990 to earn tour-level wins outside of Davis Cup competition on every surface to shave no less than 200 spots off his ranking, thanks to a game that has continued to evolve.
At 18 years and 25 days, he became the youngest Challenger champion of the season and the fifth-youngest German winner in history when he stormed to his maiden ATP Challenger title on home soil in Hamburg by beating Federico Cina 7-5, 7-6(4) in the final.
In addition, Engel became the first player born in 2007 or later to win an ATP Tour match when he defeated Coleman Wong in Almaty, which prompted increased media attention in his home country.
Engel's playing style is characterised by powerful, aggressive baseline play, featuring a big serve and strong backhand, complemented by significant mental toughness and athleticism. He is drawing inspiration from idols like Nadal and Djokovic to become a well-rounded, hard-hitting competitor who seeks to control points with power and consistent groundstrokes.
Eliot Spizzirri
It's unusual to see somebody jump more than 600 spots in the world rankings, but the 23-year-old American Eliot Spizzirri has accomplished that feat over the course of just 10 months.
As an all-round player who controls pretty much all aspects of the game and possesses an impressive variety of shots, he has improved his ability to finish points from the baseline.
At ATP level, he already proved that he is closing in on being able to compete with the best when he reached the quarter-final in Brussels, defeating Alexander Blockx, Pedro Martinez, and Botic van de Zandschulp, before coming up short in a tight match against eventual champion Felix Auger-Aliassime.
After reaching the second round of the US Open in 2021, Spizzirri decided to undergo surgery to relieve himself of consistent wrist pain. It forced him to seek alternative ways of developing his game, which had a positive effect on his playing style as he raised his level in terms of breaking serve and also improved his first-serve percentages.
So don't be surprised if you find Spizzirri breaking into the top 75 or 50 in the season to come.
Learner Tien
Michael Chang became the youngest male player ever to win a Grand Slam singles title, achieving this at the 1989 French Open at just 17 years, three months, and 20 days old (or 17 years, 109-110 days), famously defeating Ivan Lendl and Stefan Edberg. Now Chang is coaching Learner Tien to follow in his footsteps, and it seems to be working.
Chang joined his team in July, providing invaluable experience and helping to accelerate his growth and all-court game. Tien began 2025 ranked No. 122 and achieved a career-high ranking of No. 28 by the end of the season.
He made a memorable run from qualifying to the fourth round of the Australian Open, becoming the youngest player to reach that stage at the hard-court major since Nadal in 2005.
Tien then won his first ATP Tour title at the ATP 250 event in Metz, defeating Cameron Norrie in the final. This made him the first American teenager to win a tour-level title since Andy Roddick in 2002.
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