THE AFL will trial a 15-second shot clock at the remaining NAB Challenge matches at Etihad Stadium, with a player's set-shot time counting down on the venue's scoreboard.  

In a move that could put tardy forwards on notice, a countdown clock will appear when the controlling umpire gives the player his 15-second warning.

It will disappear when the player starts his approach, with the umpire calling time on as normal once it reaches zero.

Players will still have a total of 30 seconds to take their set shot before play on is called.      

The shot clock is one of a number of initiatives being tested at Etihad Stadium before the start of the season, which will improve "interaction and understanding of the game" for supporters. 

Football managers were made aware of the trials last week, with the League confirming the details in a memo to clubs on Tuesday afternoon. 

The AFL limited the time available to players taking a set shot in 2006, setting the 30-second limit as part of changes designed to make the game more fluent.

As well as the countdown clock, fans at Etihad Stadium for this week's matches will hear umpire explanations of free kicks and score reviews.

The free kick explanations will be broadcast during scoreboard replays, while the umpire's verdict during score reviews will be broadcast on the ground's PA.  

St Kilda and Hawthorn kick off the final round of NAB Challenge matches on Thursday night at Etihad Stadium before Melbourne and Essendon square off at the venue one night later.

There is a double-header at the stadium on Saturday, with Richmond taking on North Melbourne during the day and Collingwood facing the Western Bulldogs in the evening.

The League will trial a new positioning of the Etihad Stadium roof for the Saturday match involving the Tigers and Bulldogs and the Sunday twilight clash between Carlton and Geelong. 

At the end of the NAB Challenge clubs, players and fans will be consulted for feedback on the trials, which won't be rolled out at other venues this pre-season.