The rules of cricketLaw 1 (The players)
1. Number of players
A match is played between two sides, each of eleven players, one of whom shall be captain.
By agreement a match may be played between sides of more or less than eleven players, but not more than eleven players may field at any time.
2. Nomination of players
Each captain shall nominate his players in writing to one of the umpires before the toss. No player may be changed after the nomination without the consent of the opposing captain.
If at any time the captain is not available, a deputy shall act for him.
(a) If a captain is not available during the period in which the toss is to take place, then the deputy must be responsible for the nomination of the players, if this has not already been done, and for the toss. See 2 above and Law 12.4 (The toss).
(b) At any time after the toss, the deputy must be one of the nominated players.
4. Responsibility of captains
The captains are responsible at all times for ensuring that play is conducted within the spirit and traditions of the game as well as within the Laws.