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Argentina and Brazil finished tied on points, so a play-off had to be played to decide the champion.
Overview
Brazil had attended the competition without two of their most notable players, defender Domingos da Guia (champion with Boca Juniors two years before) and striker Leonidas da Silva, nicknamed the Black Diamond. The tournament was played in a single round-robin system, but Argentina and Brazil finished tied on points, meaning a playoff match was required to determine a champion, according to the rules in force.
The match was held in San Lorenzo stadium, were both teams played hard, committing several number of fouls. After Brazilian player Domingos Spitalletti kicked Francisco Varallo violently in the 36th minute, a riot involving all the players (even some substitutes) started. After a hiatus of 40', the match restarted. Nevertheless, just two minutes a new riot happened after Cunha hit Cherro on his face.
As the score was tied 0–0 when 90 minutes expired, two 15-minute halves of extra time were required to determine the champion: during the extra time, de la Mata scored two goals within four minutes, allowing Argentina to win its fifth South American championship.
When I was substituted vs Uruguay, I became demoralised. Still sweated, I stayed to watch the second half. Then I got ill, probably with bitterness. I scored the two goals but I wanted to play more time. I didn't.
— Vicente de la Mata, during an interview with El Gráfico