Early life
Rivera was born in Panama City, Panama on November 29, 1969 to Mariano, Sr., a ship captain in the fishing industry, and Delia. Rivera grew up in the Panamanian fishing village of Puerto Caimito, frequently playing soccer with his friends. They also played baseball in the streets by substituting milk cartons for gloves and tree branches for bats, and taping beat-up baseballs. Rivera used this makeshift equipment until his father bought him his first leather glove when he was 12 years old. He thought of baseball as a pastime and did not seriously consider playing professionally. After graduating from Pablo Sanchez High School at age 16, he worked 12-hour days on a commercial shrimping boat on which his father was captain. Rivera did not consider taking up the profession as an adult, though, calling the job “way too tough”. As a 19-year-old, he had to abandon a capsizing 120-ton commercial boat, all but convincing him to give the job up.