#NextGenATP stars Tien & Fonseca spring biggest Grand Slam upsets of 2025
To mark the end of another thrilling season, ATPTour.com is unveiling our annual ‘Best Of’ series, which will reflect on the most intriguing rivalries, matches, comebacks, upsets and more. Today we highlight five standout Grand Slam comebacks from this season.
Taking down a top player is one thing, but doing it on their favourite surface, in front of a packed crowd — or even in your first Grand Slam match — is something else.
From rising teenagers dismantling top seeds to qualifiers defying the odds on the sport’s grandest stages, the 2025 majors delivered drama few could have scripted. As part of our annual season-in-review series, ATPTour.com counts down the five most unexpected Grand Slam upsets of the year.
[ATP AWARDS]5) Roland Garros R2: Gigante d. Tsitsipas 6-4, 5-7, 6-2, 6-4
Stefanos Tsitsipas had turned Roland Garros into one of his happiest hunting grounds, until Matteo Gigante kicked the doors down.
Few expected the Italian qualifier, at No. 167 in the PIF ATP Rankings, to trouble one of the clay-court elite. But Gigante, playing with the verve and fire of someone who had nothing to lose, unleashed his explosive lefty forehand to topple the 2021 finalist in four sets. It was a loss that cut deep for Tsitsipas.
For the first time since 2018, the former World No. 2 and Nitto ATP Finals champion fell outside the Top 20, and his season was later derailed by a back injury that limited him to just four more wins. Gigante’s run to the third round was a defining moment, and the Italian has since risen to a career-high World No. 125 as he continues his bid for a Top 100 berth.
<img alt=”Matteo Gigante” style=”width:100%;” src=”/-/media/images/news/2025/11/18/14/09/gigante-roland-garros-2025-upsets.jpg?w=100%25″ />Matteo Gigante earns his first Top 20 win over Stefanos Tsitsipas at Roland Garros. Photo: Adam Pretty/Getty Images.
4) US Open R2: Collignon d. Ruud 6-4, 3-6, 3-6, 6-4, 7-5
For Raphael Collignon, New York became the city where promise met proof.
A broken thumb had disrupted his aim of gaining direct entry to Roland Garros, and until the US Open, he had never won a main-draw match at a major. But, after downing Daniel Elahi Galan in his opener, Collignon then produced the performance of his life to prevail against the 2022 finalist Casper Ruud after three hours and 28 minutes.
“I think it’s the best day of my life,” said Collignon. “It was not easy because Casper is a great champion. I was so scared at the beginning, but I found my rhythm.”
It wasn’t all straightforward for Collignon, however, as he served three double faults when serving for the match at 6-5 in the fifth before eventually converting his third match point. It was a win that catapulted him back inside the Top 100 and set him up for a strong finish to the year, during which he overcame No. 8 Alex de Minaur in the Davis Cup and reached the semi-finals on home soil at the ATP 250 in Brussels.
<img alt=”Raphael Collignon” style=”width:100%;” src=”/-/media/images/news/2025/11/18/14/29/collignon-us-open-2025-upsets-2.jpg” />Raphael Collignon reaches the third round at a major for the first time. Photo: Matthew Stockman/Getty Images.
3) Wimbledon R1: Rinderknech d. Zverev 7-6(3), 6-7(8), 6-3, 6-7(5), 6-4
After four hours and 44 minutes on Centre Court, Arthur Rinderknech delivered the moment that would change the rest of his 2025 season. The Frenchman’s opener against third seed Alexander Zverev at Wimbledon had all the makings of a mismatch, but he refused to play the part of underdog.
Rinderknech slammed 79 winners with relentless aggression, taking it to Zverev from the first ball to the last to secure his maiden win over a Top 5 player. The upset became a springboard for a stunning second half of the season, which included a semi-final run in Gstaad and a fourth-round showing at the US Open. He later reached his maiden ATP Masters 1000 final in Shanghai where, fittingly, he defeated Zverev again and improved to 2-0 in their Lexus ATP Head2Head series.
“It was a very important moment, probably the best tennis moment of my career,” Rinderknech said in October, speaking of his Wimbledon win against Zverev. “Then several things succeeded step by step. I feel I’m on the right track and I can now do what I want to do, the way I want.”
<img alt=”Arthur Rinderknech” style=”width:100%;” src=”/-/media/images/news/2025/11/18/14/05/rinderknech-wimbledon-2025-upsets.jpg” />Arthur Rinderknech defeats Alexander Zverev in five sets at Wimbledon. Photo: Corinne Dubreuil.
2) Australian Open R1: Fonseca d. Rublev 7-6(1), 6-3, 7-6(5)
Joao Fonseca arrived at the Australian Open as one of the Tour’s most exciting prospects, but few expected him to out-hit one of the sport’s fiercest ballstrikers in his first main-draw match at a major.
Yet Fonseca used his calm aggression and heavy forehand to surge past ninth seed Andrey Rublev in straight sets — a win that electrified Margaret Court Arena and set social media alight. For the 18-year-old Brazilian, who had triumphed at the Next Gen ATP Finals presented by PIF four weeks prior, it was validation of months of hype following his rapid climb across the 2024 season.
“I was trying to not put pressure on myself, playing with a Top 10 guy in a huge stadium,” said Fonseca, who was backed by many Brazilian fans in Melbourne. “[I was] trying to call the crowd to help me. I just enjoyed playing my game. That’s one thing about myself, is that I play better in the important points, I go for my shots. That was the difference today.”
<img alt=”Joao Fonseca” style=”width:100%;” src=”/-/media/images/news/2025/11/18/14/16/fonseca-melbourne-2025-upsets.jpg” />Joao Fonseca beats Andrey Rublev in straight sets at the Australian Open. Photo: William West/Getty Images
Although Fonseca fell in his second-round match to Lorenzo Sonego, the young talent has further proven himself across the 2025 season. He captured his maiden ATP Tour title in Buenos Aires in February and then won the crown at the ATP 500 in Basel, becoming the first Brazilian to win a title above ATP 250 level since Gustavo Kuerten in 2001.
1) Australian Open R2: Tien d. Medvedev 6-3, 7-6(4), 6-7(8), 1-6, 7-6(10-7)
Margaret Court Arena played host to two of the season’s biggest shocks, and American teenager Learner Tien delivered the second with his marathon, late-night victory over three-time Australian Open finalist Daniil Medvedev.
Competing as the World No. 121, Tien looked destined for a heartbreak chapter rather than a breakthrough one after failing to convert a match point in the third set. The tension escalated further into the night when Medvedev stepped up to serve for the match at 6-5 in the fifth, but Tien refused to wilt, showing a blend of courage and clarity — and even shades of Medvedev’s own tactical shrewdness — to claw his way back and seize the biggest win of his career at 2:54 a.m. local time.
“I was definitely hoping it wouldn’t go to a fifth-set breaker, but I’m just happy to get a win,” said Tien. “I know I made it a lot harder than maybe it could have been… Losing the third was tough after playing for that long and having a match point.”
<img alt=”Learner Tien” style=”width:100%;” src=”/-/media/images/news/2025/11/18/14/20/tien-melbourne-2025-upsets.jpg” />Learner Tien defeats Daniil Medvedev in five sets at the Australian Open. Photo: Paul Crock/Getty Images.
From there, Tien’s trajectory only grew steeper. Along with Fonseca, who defeated the American in the 2024 Next Gen ATP Finals presented by PIF title match, Tien suddenly looked fully at home at tour level. He amassed five Top-10 wins across 2025, according to the Infosys ATP Win/Loss Index, and captured his first ATP Tour title in Metz in November.
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