Five stunning upsets in the 2025 Grand Slam season: Fonseca, Lenachen, and other dark horses' comeback stories

To commemorate yet another exciting season finale, ATP’s official site (ATPTour.com) has introduced the yearly “Best of” recap series, focusing on the season’s most notable clashes, tournaments, reversals, and surprises. Today, we kick off with the top five jaw-dropping upsets from this year’s Grand Slam tournaments.

Defeating a top player is already challenging, but doing so on their favorite surface, in front of a full crowd—especially during one’s first Grand Slam main draw match—is even more remarkable.

From emerging teenagers toppling seeded players to qualifiers breaking through on tennis’s biggest stages, the 2025 Grand Slams delivered a series of unexpected dramatic moments. As part of the season review, ATP.com reveals the five most surprising Grand Slam upsets of the year.

Fifth place: French Open second round – Gigante 6-4, 5-7, 6-2, 6-4 defeats Tsitsipas

Tsitsipas had made Roland Garros his favorite hunting ground untilMatteo Gigantechanged everything.

Few expected the Italian qualifier ranked only 167th to trouble this clay-court specialist. But Gigante, fueled by a “no retreat” determination and explosive left-handed forehand, overcame the 2021 French Open finalist in four sets. This loss hit Tsitsipas hard—marking his first drop out of the top 20 since 2018 and followed by a back injury that limited him to just four more wins that season. Meanwhile, Gigante reached the third round, a career milestone, and climbed to a career-high ranking of 125, continuing his push toward the top 100.

Matteo Gigante’s first French Open victory over a top 20 player Tsitsipas

Fourth place: US Open second round – Colinion 6-4, 3-6, 3-6, 6-4, 7-5 defeats Ruud

ForRaphael ColinionNew York became the city where “dreams turned into reality.”

A thumb injury disrupted his direct entry to Roland Garros, and before this US Open, he had never won a main draw Grand Slam match. But after beating Daniel Elahi Galan in the first round, Colinion delivered the best performance of his career in round two, defeating 2022 US Open finalist Casper Ruud in a 3-hour 28-minute battle.

“This is definitely the best day of my life,” Colinion said. “Winning wasn’t easy because Casper is a great champion. I was nervous at first but gradually found my rhythm.”

Colinion’s path to victory was far from smooth—leading 6-5 in the fifth set with a chance to serve for the match, he committed three double faults but finally converted on his third match point. This win brought him back into the top 100 and laid the foundation for a strong season finish: he later beat world No. 8 Alex de Minaur in the Davis Cup and reached the semifinals at his home ATP 250 event in Brussels.

Raphael Colinion reaches Grand Slam third round for the first time

Third place: Wimbledon first round – Lindgren-Nehi 7-6(3), 6-7(8), 6-3, 6-7(5), 6-4 defeats Zverev

After a grueling 4-hour 44-minute battle on Centre Court, Arthur Lindgren-Nehi experienced a turning point that shaped the rest of his 2025 season. The French player faced third seed Alexander Zverev in the first round, widely expected to be a one-sided match, but he refused to play the underdog.

Lindgren-Nehi unleashed relentless attacking power, hitting 79 winners and applying pressure from the first to the last point, ultimately securing his first career victory over a top 5 player. This upset became a springboard for his season’s second half: he reached the semifinals in Gstaad, the fourth round at the US Open, and made his first Masters final at the Shanghai ATP 1000 event—where he again defeated Zverev, improving their head-to-head to 2-0.

“That was a crucial moment and probably the best tennis memory of my career,” Lindgren-Nehi said in October reflecting on his Wimbledon win. “Everything went smoothly afterward. I knew I was on the right path and could now play the tennis I wanted in my own way.”

Arthur Lindgren-Nehi’s five-set victory over Zverev at Wimbledon

Second place: Australian Open first round – Fonseca 7-6(1), 6-3, 7-6(5) defeats RublevRublev

João Fonseca entered the Australian Open as one of the most anticipated young talents on tour, but few expected this Grand Slam debutant to gain the upper hand against one of the game’s most explosive hitters.

Yet Fonseca, with his composed attacking style and heavy forehand, defeated ninth seed Andrey Rublev in straight sets. This win ignited the crowd at Margaret Court Arena and caused a social media sensation. The 18-year-old Brazilian, who had won the 2024 Next Gen ATP Finals just four weeks earlier, proved that the rapid rise he made in 2024 was no fluke.

“I tried not to put pressure on myself playing against a top 10 player in such a big stadium,” Fonseca said, cheered on by many Brazilian fans in Melbourne. “I worked to engage the crowd and get them behind me. I just enjoyed the match—the biggest advantage I have is my willingness to fight on crucial points, which was key to winning today.”

João Fonseca’s straight-sets victory over Andrey Rublev at the Australian Open

Although Fonseca lost to Lorenzo Sonego in the second round, the young prodigy continued to prove himself throughout the 2025 season: in February, he won his first ATP Tour title in Buenos Aires, then captured the ATP 500 title in Basel, becoming the first Brazilian to win an ATP 250 or higher event since Gustavo Kuerten in 2001.

First place: Australian Open second round – Lenachen 6-3, 7-6(4), 6-7(8), 1-6, 7-6(10-7) defeats Medvedev

Margaret Court Arena witnessed two of the biggest upsets this season, including a marathon late-night battle where American teenagerLenachendefeated three-time Australian Open finalist Daniil Medvedev in a stunning upset.

Ranked 121st at the time, Lenachen had match point in the third set but failed to convert, seemingly headed for a heartbreaking loss rather than a career breakthrough. As the night deepened and tension mounted—Medvedev serving for the match at 6-5 in the fifth—Lenachen showed courage and composure, even demonstrating tactical savvy reminiscent of Medvedev himself, ultimately turning the match around to win at 2:54 a.m. local time, marking the most significant victory of his career.

“Of course, I wished not to play a fifth-set tiebreak, but I’m happy to have won the match,” Lenachen said. “I know I made it harder than it needed to be… losing the third set after having match point was really tough.”

Lenachen’s five-set victory over Daniil Medvedev at the Australian Open

Since then, Lenachen’s career trajectory has soared. Like Fonseca, who defeated him in the 2024 Next Gen ATP Finals final, Lenachen has suddenly established himself on the tour. According to the Infosys ATP Win/Loss Index, he secured five top 10 wins in 2025 and claimed his first ATP Tour title at the Metz event in November.

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