WHEN the substitute was reintroduced for the 2021 season after a five-year hiatus, there was a suggestion from some coaches that it should be restricted to players aged under 21.

For some clubs, that is still the most effective use most weeks. But for others, the substitute role has become one best filled by an experienced player who can provide guidance and a cool head on the bench before making an impact on-field late in the game.

Last Saturday night's clash between Fremantle and North Melbourne provided a clear contrast in how clubs can choose to use the substitute in 2025, with a veteran inside midfielder up against a 14-game speedster.

The Dockers have used dual Brownlow medallist Nat Fyfe as their substitute for the past two weeks with great success as the midfielder has resumed after a long layoff with knee and hamstring injuries.

The Kangaroos, meanwhile, opted for Robert Hansen Jnr, who sparked the team late with three direct goal assists among his dashing seven disposals and a game-high four score involvements in the final quarter.

Fyfe is among a handful of veterans who have been used in the substitute role this season, alongside Collingwood champion Scott Pendlebury, Greater Western Sydney midfielder Callan Ward, Geelong premiership star Mitch Duncan, and former Gold Coast skipper David Swallow.

 The challenge for all clubs, however, when they find a player who performs the role well is that it has a time limit, given players need to play a full game at some stage to maintain match fitness and form.

"Gut feel is you can only be sub for so long," coach Justin Longmuir said this week.

"We've had players who were sub for three weeks in a row and we probably feel like that is the max."

With Fyfe filling the role for two weeks, the Dockers rank fourth for the average age of their substitutes this year (26.0).

Bailey Banfield, who can play forward, back or wing, has also filled the role multiple times and is 27, while James Aish (29) and Quinton Narkle (27) are among more experienced players to fill the role.

Hawthorn became a statistical outlier last year when triple-premiership forward Luke Breust emerged as a specialist substitute, playing the role 12 times in two six-game stretches, the second of which included both of the Hawks' finals.

They finished the season with an average age of 28.3 for their substitutes, which was the highest recorded by any team since the role was reintroduced for the 2021 season and well above the competition average of 24.4 last year.

This year that average for the Hawks has dropped to 26.8, but their substitutes remain the equal oldest in the AFL with Collingwood (26.8), and the most experienced by games played (109.9).

There are many different factors that contribute to which player is selected as a substitute, according to coaches. Most notable is team balance and which position on the ground requires insurance.

It's why versatile players like Banfield make good substitutes, but also why Chris Fagan selected ruck Darcy Fort as a substitute in 2022, knowing the team's biggest risk was taking Oscar McInerney in as a solo big man against Paddy Ryder and Rowan Marshall.

Management of minutes also plays a prominent role when players are returning from injury, like in the recent case of Fyfe and the selection of Tom De Koning by Carlton as a substitute in the elimination final against Brisbane last year.

When it comes to tactical selections, players classified as general forwards by Champion Data remain the most popular substitutes in 2025.

It is clear in 2025 that coaches do not like the rule and they have been comfortable speaking out about it and pushing for five players on the interchange bench instead.

The position causes complications, like pulling the trigger early and then having an injury. Adelaide coach Matthew Nicks has been among coaches who have liked to be aggressive with the role.

It can also work the other way if coaches choose to be conservative but wait too long and then have a young player set back by a lack of game time during their development. West Coast coach Andrew McQualter has found himself in this position in 2025 after draftee Bo Allan played minimal minutes in rounds 12-13.

The Eagles, however, have been among the more fortunate clubs when it comes to substitute use, having the luxury in all but three games to use it in a tactical manner, behind only the Crows (one).

Greater Western Sydney and Port Adelaide are at the other end of the scale, being forced into using the substitute early to replace an injured player in more than half of their games.