Complex sentence: There have been 18 head coaches of the San Antonio Spurs National Basketball Association (NBA) franchise, which was founded as the Dallas Chaparrals of the American Basketball Association (ABA) in 1967.
Split into simpler sentences: There have been 18 head coaches of the San Antonio Spurs franchise, formally known as Dallas Chaparrals. The San Antonio Spurs started out as the Dallas Chaparrals who played in the American Basketball Association (ABA) in 1967.