The AFL has announced that clubs will be able to replace an injured or concussed player under a new medical substitute rule on the eve of the 2021 AFL Premiership season.

Clubs will name a 'normal' squad of 22 players and four emergencies the evening before the game, but they won't have to name the 23rd 'medical substitute' player until final teams are confirmed an hour before the first bounce.

The extra 23rd player will only be able to take the field after club doctors have assessed an injured or concussed player as 'medically unfit' to continue in the match.

Club doctors must provide the AFL with a medical certificate on the first working day after the match as evidence the substituted player was not medically fit to continue.

Any club found to be breaking the medical substitute rule can be sanctioned "for conduct unbecoming, or prejudicial to the interests or reputation of the AFL, or to bringing the game of football into disrepute”.

St Kilda Chief Operating Officer Simon Lethlean welcomed the decision by the AFL.

“The introduction of the medical sub demonstrates the AFL’s commitment to the health and safety of players,” said Simon Lethlean.

“Whether its managing a concussion or another game day injury or medical issue, this rule gives club’s ability to best manage medical issues on the day while still being able to be as competitive as possible."

The rule will not be implemented in the 2021 NAB AFW, VFL, VFLW or NAB League Competitions.

Read the full AFL Statement.