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The 19 year-old played fearlessly in the biggest match of his life to earn a 6-3, 6-4 victory in Basel against Davidovich Fokina, who holds a 0-5 record in tour-level finals.

Fonseca is the first Brazilian to win a title above ATP 250 level since Gustavo Kuerten clinched the ATP Masters 1000 crown in Cincinnati in 2001, while he is the third-youngest player to win an ATP 500 title since the series began in 2009.

"It is crazy. I want to thank my family and my coaches who helped me achieve this amazing effort," Fonseca said. "My parents just came from Brazil. 

"They were coming to Paris and changed their flights and came here one hour before the match with my uncles. It is just amazing to have them here for the biggest title of my career. It is a pleasure playing this sport and this tournament and I am very happy."

Fonseca’s victory in Switzerland marks the latest breakthrough moment in his flourishing early career. The 19 year-old won the NextGen ATP Finals title in Jeddah last December and then captured his first Top 10 win at the Australian Open, where he beat Andrey Rublev.

Title success followed at the ATP 250 in Buenos Aires, where he became the youngest South American champion in the ATP Tour Era (since 1990). Fonseca will climb to a career-high No. 28 in the ATP Rankings with this latest triumph, having started the year at No. 145.

"They were the ones that believed in me," Fonseca said when asked about his parents. "I was thinking about going to university and they said it was my choice and they would be there to support me. I just want to thank them. Since I was young, my mum travelled with me. Since I was 11, I only travelled with her, so that title is for her."

In a high-quality performance, Fonseca clubbed 15 winners in the first set, rushing Davidovich Fokina, who struggled to cope with the Brazilian’s power. The 19 year-old stood close to the baseline to dictate and converted on his fourth set point to lead. 

Fonseca continued to pile on the pressure in the second set and closed out on serve after failing to convert a championship point on return at 5-3. The 19-year-old leads the Spaniard 2-0 in the pair's Lexus ATP Head2Head series following his 86-minute victory.

Fonseca struck 28 winners to 19 unforced errors and struck his forehand at an average of 81 mph, six mph faster than Davidovich Fokina. Fonseca is 25-15 on the year.

Davidovich Fokina has now lost four finals in 2025 and five overall. He squandered two championship points against Miomir Kecmanovic in Delray Beach and then three against Alex de Minaur in Washington. The 26 year-old also fell in the title match in Acapulco to Tomas Machac.

Despite his latest heartbreak, the Spaniard is up to No. 15 in the  ATP Live Rankings.