Raised in the modest Panamanian fishing village of Puerto Caimito, Rivera was an amateur player until he was signed by the Yankees organization in 1990. He debuted in the major leagues in 1995 as a starting pitcher, before permanently converting to a relief pitcher late in his rookie year. After a breakthrough season in 1996 as a setup man, he became the Yankees' closer in 1997. In the following seasons, he established himself as one of baseball's top relievers, leading the major leagues in saves in 1999, 2001, and 2004. Rivera primarily threw a sharp-moving, mid-90s mile-per-hour cut fastball that frequently broke hitters' bats and earned a reputation as one of the league's toughest pitches to hit. With his presence at the end of games, signaled by his foreboding entrance song "Enter Sandman", Rivera was a key contributor to the Yankees' success in the late 1990s and early 2000s. An accomplished postseason performer, he was named the 1999 World Series Most Valuable Player (MVP) and the 2003 AL Championship Series MVP, and he holds several postseason records, including lowest earned run average (ERA) (0.70) and most saves (42).