Complex sentence: The Seattle Mariners, a Major League Baseball franchise from Seattle, Washington, that plays in the American League West division, has used 15 different Opening Day starting pitchers in its 32 seasons.
Split into simpler sentences: The Seattle Mariners are a Major League Baseball franchise from Seattle, Washington who play in the American League West division. The Mariners have used 15 different Opening Day starting pitchers in its 32 seasons.