Can a player who has been replaced come back on?

Question

Accepted Answer

An injured player who is permanently replaced can't return. A player taken off tactically (for example, a starting prop subbed in the second half) may come back on only to replace: an injured front-row player; a player with a blood injury; a player with a head injury; a player just injured by foul play (as confirmed by the match officials); a player nominated to leave so a front-row player can come on when a front-rower has been carded or sent off; a teammate who received a 20-minute red card, once 20 minutes of playing time have passed (elite rugby only). All replacements happen only when the ball is dead and with the referee's permission (World Rugby Law 3).