Complex sentence: The competition replaced the short lived Football League Group Cup competition which was only played between 1981/2 and 1982/3 (although confusingly, in the second year it was also called the Football League Trophy).
Split into simpler sentences: The competition replaced the short lived Football League Group Cup. A competition which was only played between 1981/2 and 1982/3 (although confusingly, in the second year it was also called the Football League Trophy).