Since August 2019, teams in international cricket have been allowed to replace a player who suffers a concussion during a match.
Like for like
The replacement must be a like-for-like swap, so a batter replaces a batter and a fast bowler replaces a fast bowler. The match referee has to approve it, and the substitute can bat, bowl and field like any other player.
The first one
The first concussion substitute in Test cricket was Marnus Labuschagne, who replaced Steve Smith during the Lord’s Test of the 2019 Ashes after Smith was struck on the neck by a bouncer. Labuschagne went on to become one of the world’s best Test batters.
The rule exists so teams are never tempted to keep a concussed player on the field just to avoid being a player short.
