Complex sentence: He appeared in 59 games for the 1962 Mets expansion team, which ended up with a record of 40-120, which continues to be the most losses by any Major League Baseball team in a single season since the 19th Century.
Split into simpler sentences: He appeared in 59 games for the 1962 Mets expansion team, which ended up with a record of 40--120. The 120 losses continues to be the most losses by any Major League Baseball team in a single season since the 19th century.