The original rules of ODI's stated that during the first 15 overs, only two fielders were allowed outside a 30 metre circle around the wicket. This meant that attacking batsman were likely to score runs quickly in the first overs, but would become more watchful at the end of the spell. In an effort to keep the game more exciting during the middle overs, the 15 over block with fielding restrictions at the beginning of the innings is reduced to 10, and thereafter, the captain of the fielding side has to decide when to bring his fielders in again for two further blocks of 5 overs, at any time he likes. These 5 over spells are called Powerplay 2 and Powerplay 3. (Powerplay 1 is the first block of 10).
The was trialled in the NatWest Challenge between England and Australia in July 2005, along with a substitution rule which has caused some controversy.
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