Football's lawmakers have defended their decision to trial permanent concussion substitutes despite pressure from leading campaigners to introduce temporary ones instead.
The International Football Association Board (IFAB) announced last week that trials would begin next month for clubs to be allowed an extra sub if medical staff suspected a player had a concussion.
But world players' union, FIFPro, have said the move fails to 'solve the problem' as medics will still have to make snap decisions on head injuries, instead of a proper 10-minute off-field assessment - as seen in rugby union - which temporary subs would allow.