Complex sentence: After a breakthrough season in 1996 as a setup man, he became the Yankees'closer in 1997 and established himself as one of baseball's top relievers, leading the major leagues in saves in 1999,2001, and 2004.
Split into simpler sentences: 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.