Complex sentence: The 1990--91 season was Cardiff City F.C. 's 64th season in the Football League when they competed in the 24-team Division Four, then the fourth tier of English football, finishing thirteenth.
Split into simpler sentences: The 1990--91 season was Cardiff City F.C. 's 64th season in the Football League. They competed in the 24-team Division Four, then the fourth tier of English football, finishing thirteenth.