Off theory in cricket is a bowling tactic that was devised in the early 19th century. Getting the batter out by removing the batter’s stumps was the most common notion in cricket’s early days. In order to do, the bowler had to bowl a straight line and length.
Changes in the laws pertaining to leg before wicket and increased skill level of bowlers led to the development of off theory. In this tactic, the bowler delivers a ball which is slightly outside the off-stump. This is called the corridor of uncertainty. The reason for this is that at the this line, the batter is often confused whether to hit the ball or leave the ball and is always at a risk of knicking it which can lead to a catch to the keeper.
The off theory increased the importance of slip and gully fielders. When a bowl is pitched in the line of off stump three situations occur. Firstly, it can either swing outwards, forcing the batter to drive and edge the ball which is carried to the slips. Secondly, it can either be left by the batter who misjudged the line of the ball, which would eventually result in the ball hitting the stumps. Finally, the bowl may swing inwards, finding a passage between the bat and pads to hit the stumps.
The off theory is a positive tactic which showcases a great contest between the bat and the bowl. It is contrasting to the now defunct leg theory, which was unsportsmanlike and fatal for the batters.