Complex sentence: He was a fan and follower of traditional American sports who had no experience with soccer until the age of 28, when he came into contact with the nascent North American Soccer League while serving as a lawyer for Jack Kent Cooke.
Split into simpler sentences: He was a fan and follower of traditional American sports. Rothenberg had no experience with soccer until the age of 28, when he came into contact with the nascent North American Soccer League while serving as a lawyer for Jack Kent Cooke.