The PFA and world players' union FIFPro have teamed up to demand football's lawmakers consider launching trials into temporary concussion substitutes.
The International Football Association Board’s (IFAB) launched trials of permanent concussion substitutions earlier this year and the Premier League introduced them from February 6.
Permanent concussion substitutes allow teams to make two permanent subs in the event of head injuries, in addition to their three regular changes.
PFA wants football's lawmakers to consider launching temporary concussion substitute trials
But the PFA and FIFPro want IFAB to launch additional trials into temporary concussion substitutes, meaning a player can be withdrawn from a game for a brief period of time before being allowed to return if they are cleared by a medic.