John Kennedy, a 21-year-old striker with many ups and downs in his short career, scored the winning goal on Saturday to give Brazil's Fluminense their maiden Copa Libertadores title against Boca Juniors.

Substitute Kennedy netted Fluminense's second goal in their 2-1 victory against the Argentinians at the Maracana Stadium in Rio de Janeiro in the ninth minute of extra time. Regular time ended 1-1.

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Kennedy was sent off for a second yellow after scoring with a powerful volley from the edge of the box, past the left corner of goalkeeper Sergio Romero. Shortly later Boca's Frank Fabra also saw a red card, which kept some balance between the two exhausted teams during extra time.

The Argentinian giants were playing for their seventh title in the tournament. Their tens of thousands of fans in Rio saw their hopes momentarily tank after their countryman Germán Cano scored in the 36th minute after a low cross from Keno.

The 35-year-old Cano netted 81 goals for the Rio-based club in 125 matches in the past two years.

Boca lost some momentum, but managed to equalize in the 72nd minute with a powerful shot by Luis Advincula from the edge of the box, a goal that allowed Argentinian fans once more to dream of the title, counting on Romero's great penalty saving skills.

Eight minutes later, Kennedy stepped in. His goal in extra time came as Fluminense pushed forward, knowing a penalty shootout could make the final go Boca's way.

The striker, who first appeared at the Rio club in 2021, struggled to get a starting position last year. He was loaned to a small club that was relegated in the Sao Paulo state league, and returned to Fluminense only months ago.

Brazilian clubs have won every edition of the Copa Libertadores since 2019, with Flamengo and Palmeiras both winning the title twice.

"I recovered the ball for my son Lorenzo. I can tell him now that I am champion of the Libertadores," said Cano, whose 13th goal this season in the competition was as many as the total scored by all of Boca's players combined.

"I want to dedicate this title to my family, the team, our director and the fans. It was a dream that we wanted to achieve since the first game," he added.

Boca, who would have tied Independiente with a record seventh title with a win, played their first continental decider since 2018. Five years ago, the yellow and blue club lost the final to archrivals River Plate, with the last match played in Madrid because of fan violence in Buenos Aires.

"We had a lot of chances today but in the end we failed to capitalise on the opportunity to take advantage of the extra man," said Boca goalkeeper Romero.

"I think we did a great cup [run], we thank the people and we regret not giving them a joy today."

The 35-year-old Marcelo, who made most of his career as a left-back but has played often as a midfielder, was one of Fluminense's keys to control the match from the start. The 19-year-old Argentinian midfielder Valentín Barco, a big hope of creativity for Boca, could not deliver in the final.

Fluminense knocked out Argentinos Juniors, Paraguay's Olimpia and its countrymen of Internacional in their path to the final, which also included a 5-1 win against River Plate in the group stage.

Boca reached the tournament's decider without winning a single match in regular time. Romero put his team forward in the ties against local Uruguay's Nacional, local rivals Racing and in the semifinals against Brazil's Palmeiras.

Fluminense reached their first Copa Libertadores final since losing the 2008 edition on penalties to Ecuador's Liga de Quito with a squad that is not among the richest in Brazil. Their coach, Fernando Diniz, is also in charge of Brazil's national team until July 2024, when local soccer executives expect to bring Real Madrid's Carlo Ancelotti to take that role into the 2026 World Cup.

The Copa Libertadores decider took place in a tense atmosphere that has dominated Rio since Thursday due to a series of brawls between fan clubs and an aggressive police response.

Tens of thousands of Argentines came to Brazil's postcard city before the encounter, including thousands with no tickets to get in. Local media reported some tried to break into the Maracana Stadium but failed.

Hotels neared maximum capacity ahead of the game, particularly in the beachside tourist areas such as Copacabana and Ipanema, according to Rio's main hotel associations.

Conmebol, the continental governing body of soccer in South America, met Friday with directors of the Brazilian Football Confederation, the Argentine Football Association, Fluminense and Boca to discuss security. Rio's military police said it deployed 2,200 officers to the match.

A fan zone was erected on Copacabana, and giant screens were placed in the city center and at the Sambodrome -- famed for the carnival parades.

The Associated Press and Reuters contributed to this report.