PFA chief executive Gordon Taylor has expressed his concern that protocol regarding concussed players was not followed in Tottenham's Barclays Premier League game with Everton on Sunday.
Spurs goalkeeper Hugo Lloris briefly lost consciousness at Goodison Park and looked visibly shaken after a collision with Everton forward Romelu Lukaku late in the second half.
Taylor commented: "I watched the incident on television and I was surprised, to say the least, that he was allowed to stay on.
"We are very concerned that the protocol that involves concussed players was not adhered to and I have raised this at the meeting with the professional game's stakeholders and the decision was taken to remind all clubs of the protocol.
"Managers should not take these decisions in the heat of the moment and that needs reinforcing."
Earlier in the week the PFA deputy chief executive John Bramhall called for players to be automatically removed from the field of play if they lose consciousness as a result of a severe trauma to the head.
Bramhall stated: "When treating a player on the pitch, it can be very difficult to determine the severity of a head injury. It is important to take the pressure off the players, club medical staff, and the manager - removing the need for them to make a very difficult decision."
"If anyone suffers a severe trauma to the head and loses consciousness, then they should be required to leave the field of play automatically."
Bramhall confirmed: "The PFA will continue to work with the stakeholders within the game to evaluate what guidelines are currently in place and to see if and how they need to be improved to provide better protection for all those involved in the game."