super sub

What was the rule?

The Super Sub used to be a direct substitute for any one player.
The Super Sub had to be named before the game began (even before the coin was tossed), and he could replace any player from the playing XI at any point in the game.
But the concept of a Super Sub was different from that of the 12th man. Unlike the 12th man, Super Sub could bat, bowl, field or keep wicket once a player was replaced.

Being a direct replacement, he couldn't bat if the player he replaced had already batted. Similarly if the player he replaced had already bowled his full quota of overs, the Super Sub couldn't bowl.