Jan Vertonghen was helped off the pitch by medical staff after appearing to lose his balance on returning to the action

Football should introduce "temporary concussion substitutions" says a brain injury charity in the wake of a head injury suffered by Jan Vertonghen.

The Tottenham defender was treated for five minutes on the pitch and tried to play on but was led off after appearing unwell during a 1-0 Champions League semi-final first-leg defeat by Ajax.

Headway says a "reliable diagnosis" cannot be made on the pitch because the "pressure is enormous and unfair, particularly in high-stake games such as Champions League semi-finals".

Spokesman Luke Griggs told BBC Sport: "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."

Tottenham 0-1 Ajax: Pochettino not involved in Vertonghen injury decision

Headway has also called for an "urgent review" into concussion protocols.

"We believe the time has come for football to introduce temporary concussion substitutions that would allow for longer off-pitch assessments to be conducted," added Griggs.

"In addition, independent doctors with expertise in concussion and head injuries should make the ultimate decision as to whether or not a player is fit to continue.

"Not every head injury will result in a concussion. 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."

Spurs boss Mauricio Pochettino said he believed medical staff followed the correct protocols before allowing 32-year-old Belgian international Vertonghen back on the pitch.

No ambulances were called to the stadium and Vertonghen was later seen walking freely through the media zone after the match.

"I wasn't involved. It was the doctor's decision," said Pochettino immediately after the game. "The rules and the protocols are there. Our medical staff followed the protocol.

"He's OK. We hope it is not a big issue. He walked away from the stadium. We know we have to keep watching and monitoring him because it was a big knock."