Australian cricketers will have to wear neck protectors on helmets when facing fast or medium pace bowling from October as part of changes to playing conditions for the 2023/24 domestic and international seasons.

Governing body Cricket Australia had recommended the use of neck protectors since the death of Phillip Hughes in 2014 but a number of top batsmen, including David Warner and Steve Smith, have resisted wearing them.

They will now have to wear them from Oct. 1 when playing at home or in international cricket overseas or face sanctions under rules to be introduced by CA.

"Protecting the head and neck is extremely important in our sport," CA's Head of Cricket Operations & Scheduling Peter Roach said in a statement.

"The neck protector product has come a long way in recent years and the decision to make them mandatory comes off the back of a lot of advice and consultation with a wide range of experts and stakeholders."

The mandate comes a week after Australia all-rounder Cameron Green was struck by a Kagiso Rabada bouncer on the neck guard fixed to his helmet and was substituted out of the first ODI against South Africa with concussion.

It was one of a raft of changes to playing conditions, which include scrapping the automatic six runs given to batters who hit the roof of Melbourne's Docklands Stadium during Big Bash League matches.

Umpires will now decide to award a six if they judge the ball would have cleared the boundary.

The use of COVID substitutes, who replaced players testing positive for the coronavirus, has also been scrapped.