UEFA's head injury protocol requires referees to stop the game to allow the team doctor to assess a player with suspected concussion on the field of play and make a decision on whether they can continue.

A three-minute window applies "in principle" for the assessment to take place, or the player should not be allowed to continue.

However, there is no provision for concussion substitutes that do not count towards a team's permitted changes within a match, which the International Football Association Board (IFAB) has allowed competition organisers to trial since December 2020.

This provision covers permanent concussion substitutions whereby a player cannot return to the field of play, although the PFA has called for temporary changes to be allowed to enable further assessment by medical staff.

UEFA has trialled concussion substitutes at last year's men's European Under-21 Championship in Hungary and Slovenia, but they did not feature at the delayed Euro 2020 tournament, in which the head injury protocol came under scrutiny when French player Benjamin Pavard was allowed to continue in a match against Germany despite later admitting he was "a little knocked out for 10, 15 seconds".

There remains no provision for them in UEFA'S club and international competitions, including the Champions League and Nations League.

The head of the PFA's brain health department Dr Adam White has called on UEFA to take immediate action.

"This situation needs to be addressed urgently," he said.

"As a bare minimum UEFA, as one of football's major bodies, must lead by example and introduce the available permanent concussion substitution rule.

"This an issue the PFA will be raising with UEFA directly."

The PFA has urged IFAB to extend its concussion substitutes trial to include temporary changes, which it says will provide additional assessment time in an appropriate environment, ensure neither team is disadvantaged when the match restarts and reduce pressure for a quick decision.

"Put simply, the current laws of the game are jeopardising player health and safety," White said.

"Permanent substitutions do not allow medical teams to assess a player with a potentially serious brain injury in an appropriate environment.

"The rules as they are create an extremely challenging situation and offer no support to medical personnel."

The latest controversy in English football came on Saturday (October 29), when Aston Villa received criticism for allowing Argentinian goalkeeper Emiliano Martínez to continue during their match against Newcastle United after taking a blow to the head, before later being replaced.