Complex sentence: The eventual World Series champions rival New York Mets finished with a Major League best 108-54 record, and finished 21½ games ahead of the Phillies and both were the only teams in the division to post winning records.
Split into simpler sentences: The eventual World Series champions rival New York Mets finished with a Major League best 108-54 record, and finished 21½ games ahead of the Phillies. The Mets and the Phillies were the only teams in the National League East to post winning records.