Complex sentence: Cassano began his professional club career with hometown club Bari, where he made a reputation for himself as one of the most promising, yet troublesome young players in Italy; his talent and performances earned him a transfer to defending Serie A champions Roma in 2001.
Split into simpler sentences: Cassano began his professional club career with hometown club Bari, where he made a reputation for himself as one of the most promising young players in Italy. His performances earned him a transfer to defending Serie A champions Roma in 2001.