Complex sentence: In 1999, at the age of 15, Silva auditioned at Madureira, Olaria and Flamengo; he was rejected at each club, the trial at Flamengo being the most difficult for he was not even observed by coaches.
Split into simpler sentences: In 1999, at the age of 15, Silva auditioned at Madureira, Olaria, and Flamengo. He was rejected at each club--the trial at Flamengo being the most difficult as Silva was not even observed by coaches.