Joao Fonseca made history after securing his maiden ATP Tour title at the Argentina Open on Sunday. (More Tennis News)
The 18-year-old overcame fifth seed Francisco Cerundolo 6-4 7-6 (7-1), becoming the youngest South American to win a title in the ATP Tour era (since 1990).
Cerundolo, playing on home soil as a native of Buenos Aires, struggled throughout an error-strewn performance, missing the chance for his fourth ATP title.
Fonseca showed the first signs of nerves when serving out the match at 5-4, and 6-5, but eventually held on for victory inside one hour and 45 minutes.
"Unbelievable week, even in Argentina there are some Brazilians cheering for me," an emotional Fonseca said. "That's just amazing.
"Every Brazilian, everyone from their country wants this support from your own country. For me, this [moment] that I'm living is just unbelievable."
The win also means Fonseca has a perfect record in tour-level finals, winning his first and only such outing after defeating a fourth Argentine of the tournament.
Data Debrief: Fonseca puts name on the map
Fonseca became the 10th-youngest title winner in ATP Tour history with this win in Argentina, aged 18 years, five months and two days.
The victory was far from expected, too, with the world number 99 becoming the lowest-ranked champion in tournament history.
Cerundolo will have no complaints after falling to one of the ATP's new stars, having been broken four times and struggling on his first serve throughout a disappointing performance.
