Normally a cricket player can only be substituted by a fielder, who is not allowed to bat or bowl. However, some competitions allow a concussion substitute who can replace a player in all aspects for the rest of the game.
The Laws of Cricket only allow substitutions in limited circumstances: for an injury or illness during the match. The substitute can only replace the player while the team is fielding and cannot bowl (though they can act as wicket keeper.)
The player who was ill or injured can come back to the game later, but (unless their absence was less than 15 minutes) cannot bowl again until they have been back on the field for as long as they were off. This prevents a team having a star bowler feign injury to preserve energy between bowling sessions.
An injury substitute cannot be used to bat. The Laws of Cricket do allow another player to act as a runner (meaning the original player bats but the runner physically runs between the wickets) but usually this will be another member of the team who has already battered, rather than a substitute. Runners are not allowed in most international matches.
The biggest exception to the Laws of Cricket (used via playing conditions) is the concussion substitute rule now used in most international matches. This means a player who suffers a concussion or suspected concussion during the game can be completely replaced by a substitute (not a player in the original starting 11) for the rest of the game. They cannot return later on (and are not allowed to play international cricket for at least seven days.)
The substitute player can bat, bowl, field and keep wicket in exactly the same way as the replaced player, though any restrictions on the replaced player (such as being banned from bowling for the rest of the game for dangerous deliveries) will apply to the substitute.
The concussion rule means that the umpires can refuse to allow somebody to act as a substitute unless that have a “comparable” role and skills. For example, somebody who is primarily a batter could not be replaced by somebody who is primarily a bowler. A specialist spinner could not normally replace a specialist fast bowler. This reduces the risk of teams taking advantage of (or even feigning) a concussion to make a tactical substitution, such as replacing a batter with a bowler after completing their innings. To allow this rule to work properly, teams must nominate five potential concussion substitutes with a range of skills.
Some local playing conditions, such as those in domestic cricket in India, allow similar substitutions in cases of serious injury where a player would otherwise have to choose between leaving their side a player short, or risking making the injury worse. This is not the case in international cricket, hence the case when Chris Woakes came out to bat at number 11 in a test match despite having dislocated his shoulder and having his arm in a sling.
Some domestic competitions allow player replacements for reasons other than concussion or injury. For example, the English County Championship allows a replacement if a player is called up to play for their country on short notice. In 2026 it began an experiment allowing a replacement for a player experiencing a “significant life event” such as a family illness, bereavement or the birth of a child.