Interchange (Australian rules football)

[11] Where a player leaves the ground on a stretcher, he is permitted to take the most direct route to the changerooms for medical treatment, and is still permitted to return later in the game; however, where he leaves on a stretcher, the player must wait for 20 minutes of playing time (the length of one regulation quarter) before returning.

If a stretcher is brought onto the ground but the player ultimately does not need to use it, he must still wait for 20 minutes before returning.

The primary means for controlling interchanges in most leagues (but not in the AFL) is via a headcount, currently detailed in Law 5.5 of the game.

If either team has more players on the ground than it should, the general rule, according to the 2019 Laws of the Game, is that any points the team had scored up to that point during the quarter of the headcount are deducted from the score and a free kick and 50-metre penalty are paid to the opposing captain from the centre of the ground or the spot of the ball.

[16] This immense penalty, which predated the interchange bench or even reserve players, was long known to be one of the great curiosities in the game's laws, and was seen so rarely that decades would usually pass without a league seeing it invoked.

In recent years, the majority of incidents of extra players on the field have been an error by a player who was meant to go to the bench after an interval, hence the shift in rules from cancelling the team's entire score to just cancelling the score for that quarter, but with the provision for further penalty as appropriate.

Ultimately, the count was abandoned when it became impossible to vouch for who was on the field at the time of the request, and West Torrens went on to win by three goals.

The other most famous headcount occurred during the Grand Final of the 2018 North East Australian Football League season between Southport and Sydney reserves.

This had an impact on the 2013 VFL season's leading goalkicker medal: Frankston's Michael Lourey finished one goal behind Port Melbourne's Dean Galea for the medal, having had one of his goals annulled in a headcount earlier in the season.

Notable successful headcounts around the country which resulted in the cancellation of a team's score are listed in the table below.

Although the AFL's laws allowed for each of the Sydney players to be fined $2500 for the error, there could be no change to the match result because North Melbourne had not called for a headcount.

This highlighted the impracticality of the head-count rule in a modern professional league with its rapid use of interchanges for fatigue management.

Other leagues have not followed this timeline: Historically, the interchange bench was used sparingly, and mostly to take poor-performing or players who were injured and unable to continue out of the game.

[33] Rule changes in the 2010s and 2020s placed restrictions on the number of interchanges, on the theory that lower fatigue levels were enabling a more defensive play style which was stifling open play and scoring, and that restricting rotations and increasing fatigue could reverse that trend.