Arsenal have been urged by concussion campaigners not to rush the return of right-back Hector Bellerin who suffered a head injury against Chelsea on Saturday.
The 21-year-old has been put on a specialist programme after colliding with Marcos Alonso during the defeat.
Bellerin was reportedly unable to answer basic questions when asked by the physio immediately after sustaining the injury.
Dawn Astle, daughter of Jeff Astle, who died of brain trauma at the age of 59 due to heading footballs, toldthe Daily Mail: "There is no room for error. There is no room for risks. No risks should be taken at all. It's better to err on the side of caution.
"I've watched the clip again. He's just out. People think of concussion, it is a bit of a wishy-washy word but it is a brain injury.
"If his arm had been broken, people can see that. But you can't see what's happening to the most fragile, complex organ in the body that once it is damaged doesn't repair itself. It's so important."
A spokesperson for Headway, the brain injury charity, said: "We were pleased to see that after concussion was suspected, the protocol was followed and the player was removed from play.
"Quite rightly, it appears he is going through the graduated return to play protocol. While this normally takes 14 days, the FA's rules state that if the player is in an enhanced care setting and as long as they pass all the necessary tests, they can return after six days.
"If the player shows any signs or symptoms of concussion during this time, they will have to begin the process again."
If Bellerin is unavailable for Saturday's game against Hull at the Emirates, there should be no concerns over his fitness for next week's Champions League last 16 first leg against Bayern Munich.