“Any injury of this nature is complex and timescales are uncertain but it’s safe to say that Raul’s most immediate needs are simple: space, rest and peace.

“Raul and his family are very thankful for the privacy they have been given, and for the overwhelming support they have felt from the football family and beyond.

“Raul is extremely grateful for all the messages of goodwill he continues to receive, which will certainly help him during his recovery.”

Brain injury association charity Headway released a statement on Monday expressing its “anger and disappointment at football’s continued failings to protect its players from concussion” and reiterated its view that temporary concussion substitutes are “urgently” needed.

Headway questioned whether Luiz would have been cleared to continue if concussion substitutes were in place.

Luke Griggs, deputy chief executive at Headway, told Sky Sports News: “When you have such serious impacts such as that, it’s hard not to suspect a concussion may have occurred.

“The protocols say, if a concussion is suspected then the player should be removed from the field of play.

“The medical teams I’m sure did things in the best interest of the player but you’ve really got to question whether these concussion protocols are fit for purpose.

“Concussion is notoriously difficult to diagnose, particularly in a pressure environment on the pitch in just three minutes. It’s an evolving injury and the symptoms can take some time to present themselves.

“We’ve been calling for football to finally move with the times and introduce temporary concussion substitutes which would allow for more detailed assessments of a player, off the pitch.

“We’ve got to make sure the message is out there that we’re not taking a chance on these things.”

The International Football Association Board (IFAB) said its Concussion Expert Group (CEG) had met on Wednesday and said it was now preparing the ground for competitions to test new protocols for concussion substitutes, with trials set to begin as early as January next year.

“The members (of the expert group) recommended further consultation, working with the FIFA medical subdivision and other stakeholders, to facilitate trials to start from January 2021 for any competition that is interested in taking part,” a statement on the IFAB website read.

The statement also said: “The CEG again emphasised that the protection of players is the main goal and that a clear and uniform approach is needed, which can operate effectively at all levels of the game.

“Therefore, the group agreed that applying an ‘if in doubt, take them out’ philosophy would be the best solution to safeguard the health of football players.”