#NextGenATP stars Joao Fonseca, Jakub Mensik and Learner Tien become first-time ATP Tour champions in 2025 | ATP Tour

ATP Tour

#NextGenATP Talents Fonseca, Mencik, Tien become first-time ATP Tour champions in 2025

Muller, Machak, Coboli, Brooksby, Diallo and Vaccello are all on the nine-man roster

December 11, 2025

To mark the end of another exciting season, ATPTour.com presents our annual “Best of” series, which will reflect the most interesting rivalries, games, comebacks, upsets and more. Today we highlight those who are joining the Circle of Winners for the first time.

The 2025 ATP Tour welcomes a new crop of first-time champions, with nine players etching their names on the winner’s list and setting the defining story of the season. The year was filled with unexpected breakthroughs, dramatic developments, and stories that captured the imagination of fans around the world.

Alexander Muller, Hong Kong
The Frenchman started the new season with a nerve-wracking win at the BOC Hong Kong Open. After defeating Kei Nishikori in the final, Alexander Muller became the third player in the Open era to win a tour-level title while losing the first set in every match (after Arthur Ashe in the 1975 WCT final and Alexander Bublik in Montpellier in 2024).

“I was a little tired on the pitch, but I think the key is to stay calm and conserve energy for yourself,” Muller said. “I stayed calm, focused on my game and tried to adapt.”

Joao Fonseca, Buenos Aires
Joao Fonseca arrived in 2025 with high expectations following his victory at the Next Generation ATP Finals presented by PIF in Jeddah last year and immediately delivered on his promise. The 18-year-old had a stellar performance at the IEB+ Argentina Open, including saving two match points in the quarter-finals against Mariano Navone, to become the youngest South American champion in the ATP Tour era (since 1990).

“It’s been an incredible week, even in Argentina I have some Brazilians cheering for me,” said an emotional Fonseca. “It’s great. Every Brazilian, everyone from their country wants the support of their country. For me, it’s [moment] It’s unbelievable that I’m still alive. “

Tomas Machak, Acapulco
Tomas Machac arrived at the Abierto Mexicano Telcel Presented by HSBC in Acapulco as the highest-ranked player yet to win a title, but he left with the ATP 500 trophy in hand. His victory in the championship game made him the only Czech players to win the title at that level, along with top ten stars Tomas Berdych and Radek Stepanek.

“It means a lot. It’s something I never dreamed would happen, especially in an ATP 500 event, so it’s awesome for me,” said Machak, who climbed five spots to No. 20 with the victory. “I’ve worked really hard over the past year so I’m happy to be able to achieve something that shows I’m on the right track.”

Jakub Mencic, Miami
Facing Novak Djokovic in the ATP Masters 1000 final would make almost anyone feel at home. But not Jakub Mensik, who turned in the best performance of his career at the Miami Open at ETA, as the 19-year-old defeated his idol in straight sets to become just the fourth man to win his first ATP Tour title at this level.

“This is not my first time against Novak,” Mencic said. Last year, he lost to Djokovic in the quarterfinals in Shanghai. “There is no more difficult task in tennis than to beat him in the final. But of course, I feel really good and it’s my time, so I’m just focused on the game like I was in the first few rounds.”

Flavio Coboli, Bucharest
Flavio Cobolli turned his 2025 season on its head in spectacular fashion at the Tiriac Open presented by UniCredit Bank. The Italian arrived in Bucharest on the back of an eight-game losing streak on the tour, but fought his way through a number of opponents, including top seed Sebastian Baez in the final, to join the ranks of ATP Tour champions.

“This is a great dream come true for my career,” Coboly said. “I have always dreamed of winning an ATP event and today it happened. I was going through a tough moment. I had never won a tournament before this event and this year, I won the event. So I’m very happy about it.”

Jason Brooksby, Houston
If Muller’s match in Hong Kong was dramatic, Jenson Brooksby’s week at the Fayez Sarofim & Co. U.S. Men’s Clay Court Championship in Houston was downright cinematic. The 24-year-old American saved match points in three games to win his first title. He won one match in the first qualifying round, two wins in the second round of the main draw against third-seeded Alejandro Tabilo, one win in the semifinals against top-seeded Tommy Paul, and finally defeated 2023 Houston champion Francis Tiafoe 6-4, 6-2 in the final. Brooksby was unranked when the season began, but in Houston he entered the tournament as world No. 507, becoming the third-lowest ranked champion in ATP Tour history (since 1990).

“It means the world. This is one of my biggest goals since becoming a professional tennis player,” said Brooksby, who entered the ATP 250 as a wild-card qualifier. “Having my first child means a lot. It really does. This is probably the best week of my life.”

Gabriel Diallo (‘s-Hertogenbosch)
At the Liberma Open, Gabriel Diallo showed off his natural feel for grass, blasting 56 aces to win the ATP 250 event in ‘s-Hertogenbosch. He collapsed from ecstasy after defeating his friend Zizou Bergs 7-5, 7-6(8) in a tense final.

“Oh my god, I have nothing to say. Winning an ATP Tour title is something you dream about since you were a kid,” said Diallo, who lost his first tour-level final in Almaty in 2024. The fact that I was able to do that here after losing the final last year means the world to me. I’m happy, not just for myself but for my whole team.

Valentin Vachero, Shanghai
Valentin Vacherot produced one of the most stunning results of the season at the Rolex Shanghai Masters. The No. 204 player in the PIF ATP Rankings, he became the lowest-ranked ATP Masters 1000 champion, defeating the likes of Holger Ruhn and Djokovic in a family-driven final, then his cousin and former Texas A&M teammate Arthur Rinderknech.

“What just happened is unreal. I don’t know what’s happening right now. I’m not even dreaming, it’s crazy,” Vaccello said after the final. “I’m very happy with the last two weeks. There has to be a loser but I think there were two winners today and one family won. I think for tennis the story is untrue.”

Learner Tian Meisi
In the final week of the regular ATP Tour season, Learner Tien created a decisive moment at the Mosel Open in Metz. The 19-year-old picked up his first tour-level trophy in a year that saw him achieve five top-10 finishes and reach the ATP 500 final in Beijing.

“I never take it for granted, just coming out here and competing. So, holding this trophy means the world to me. I’m really grateful,” Tian said during the trophy ceremony.