The 'concussion substitution' rule allows a team to replace a concussed player in the nominated team

Marnus Labuschagne of Australia became the first player to be used as a substitute under the new set of ICC guidelines after replacing Steve Smith in the 2nd Ashes Test at Lords

A team can apply to the match referee to have a 'like-for-like' replacement in case of a concussion to any player during a match