Complex sentence: William Ernest Walsh (November 30,1931--July 30,2007) was the head coach of the San Francisco 49ers and the Stanford Cardinal football team, during which time he popularized the West Coast offense.
Split into simpler sentences: William Ernest Walsh (November 30,1931--July 30,2007) was an American football coach. He served as the head coach of the San Francisco 49ers and the Stanford Cardinal football team, during which time he popularized the West Coast offense.