A brain injury charity has renewed calls for football's authorities to introduce "temporary concussion substitutions" in the wake of Jan Vertonghen's severe-looking head injury during Tottenham's Champions League semi-final with Ajax.
Rising to win a ball with Toby Alderweireld, the 32-year-old was left bloodied and was treated for several minutes before being allowed to continue.
Referee Antonio Mateu Lahoz spoke to Spurs' medical staff before allowing Vertonghen to return to the field, only for the defender to quickly go off again.
Manager Mauricio Pochettino had to put his arm around to help keep the groggy defender up, before he was carried away after appearing to wretch by the touchline.
Vertonghen has since been given the all-clear by Spurs, who say he had not suffered concussion, and walked unaided out of the Tottenham Hotspur Stadium afterwards.
But the focus is now on how the Belgian international defender was allowed back on the pitch, given his poor state when he had to go off again shortly afterwards.
Charity Headway say protocol needs to be introduced to allow medical staff to make proper assessments of injured players in situations like Vertonghen's.
"We believe the time has come for football to introduce temporary concussion substitutions that would allow for longer off-pitch assessments to be conducted," said spokesperson Luke Griggs.
"It is hugely disappointing that we are once again talking about concussion rather than the game itself.
"Concussion is notoriously difficult to diagnose. The symptoms may be hidden and require the individual to be honest about how they're feeling, while they can also be delayed in their presentation.
"Assessing a player for three minutes - or even five, as was the case with Jan Vertonghen - does not allow for medical staff to make a reliable diagnosis, particularly when this is conducted on the pitch under the gaze of tens of thousands of fans eager for the game to resume.
"The pressure on club medical staff is enormous and unfair, particularly in such high-stakes games such as a Champions League semi-final."
In addition to the temporary substitutions, Headway want "independent doctors with expertise in concussion" to make the final decision on whether players are fit to continue.
"Not every head injury will result in a concussion," Griggs added. "But allowing players to continue while showing clear signs of discomfort following a head injury is contrary to the 'if in doubt, sit it out' principle at the heart of all effective concussion protocols."
Uefa implemented new concussion procedures across all of its competitions following approval by the Executive Committee in September 2014.
Champions League regulations state: "Any player suffering a head injury that requires assessment for potential concussion will only be allowed to continue playing after the assessment, on specific confirmation by the team doctor to the referee of the player's fitness to do so."
Tottenham were criticised in November 2013 after goalkeeper Hugo Lloris was allowed to remain on the pitch against Everton after being knocked out in a collision with Romelu Lukaku's knee and initially being unable to remember where he was.
Additional reporting by PA
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