Jimenez was knocked unconscious after an accidental collision with Brazilian Luiz who rather surprisingly played on until half-time with blood seeping through a head bandage.

Jimenez, 29, needed oxygen on the pitch and was taken to hospital for scans, eventually undergoing surgery for the skull fracture.

Luiz was substituted at half-time.

While Arsenal insisted they followed Football Association protocols for head injuries in allowing 33-year-old Luiz to play on, the situation raised questions about whether enough was being done to safeguard players' welfare.

The FA is considering fast-tracking a trial of concussion substitutions in the FA Cup as early as December.

Liverpool boss Juergen Klopp says he would support such a move.

"I know we have concussion protocols and I'm pretty sure Arsenal did that. I'm not sure any rule would help in that moment because the player can play on," Klopp said on Monday when asked about concussion substitutes.

"But, yes, it makes sense that we can do things like this."

Former England captain Alan Shearer, who recently hosted a documentary about possible links between a career heading a football and dementia, said a change was long overdue.

"Football needs to get real, it needs to wake up, it needs to get serious. Not next year, next month, now. It's not acceptable, it has been going too far too long," he told the BBC.

"They're on about trialling concussion substitutes. What is there to trial? It's been going on for years. It's not acceptable."

Manchester City's Brazil goalkeeper Ederson, who suffered a head injury while playing against Liverpool in 2017, said such situations required special attention.

"When there is a blow to the head there should be a substitution, whether the player can continue or not. You could be feeling okay but after you could feel the consequences."

FA rules state that if there is any suspicion of a player having sustained a concussion, the player must be removed from the field of play, and not allowed to return.

Australian Associated Press