Complex sentence: The Athletics have been to 26 National Superior Basketball (BSN) Finals, of which one was cancelled (1953) due to confiscation because of a fight between players from San Germán and the Ponce Lions, giving birth to Puerto Rican basketball's most intense rivalry.
Split into simpler sentences: The Athletics have been to 26 National Superior Basketball (BSN) Finals. Of which one was cancelled (1953) due to confiscation because of a fight among players of San Germán and the Ponce Lions, giving birth to Puerto Rican Basketball's most intense rivalry.