CNN  — 

Former Major League Soccer star Taylor Twellman knows the dangers of head injuries and their lingering effects better than most.

Now 39 and working as media pundit for ESPN, the former New England Revolution forward was forced to retire from the sport due to multiple concussions following a devastating 2008 collision with LA Galaxy goalkeeper Steve Cronin.

And as he looks back at the injury suffered by Tottenham’s Jan Vertonghen in Tuesday’s Champions League semifinal, Twellman, who set up a foundation to raise awareness of the dangers of concussion, is troubled by what he saw.

Vertonghen was left bloodied and dazed after colliding with teammate Toby Alderweireld as the pair challenged Ajax goalkeeper Andre Onana for the ball.

“I got sick to my stomach,” the 39-year-old Twellman told CNN about his reaction to the collision and the aftermath.

After being treated on the field for some time, Vertonghen was initially cleared to continue playing, before staggering to the touchline just moments later. There, he stood retching and had to be helped from the field by the team’s backroom staff.

Jan Vertonghen was initially given the all-clear to continue playing, before being helped off the field just moments later.

“Hopefully no one has to die,” said Twellman of what he sees as football’s troubling record on responding to head injuries.

“It’s irresponsible, it’s disgusting, and quite honestly it’s pathetic that we’re still having this conversation in 2019.”

Tottenham said its medical team strictly followed the English Football Association concussion guidelines in caring for Vertonghen. In a statement, the club said, “Following testing he was judged to be alert and answered all questions correctly and lucidly, deeming him fit to return to the field of play.

“All available video footage was relayed to our on-pitch medical team and they were able to confirm that he had suffered no loss of consciousness.”

Speaking earlier on Thursday in a press conference, Spurs manager Mauricio Pochettino reiterated his defense of his medical team, stating: “We followed the protocol.”

He added: “Our doctor and medical staff behaved very well, they were excellent, followed the protocol. I respect [their decisions] because I think I’m professional about football, not medicine. All decisions about health are for medical staff.

“The assessments on concussion were negative, that’s why the player was allowed to play. A few seconds after that was a completely different thing, he [started] to feel no good. After that, we changed in that moment, and he was out of the pitch.

Vertonghen had to be helped off the pitch by his manager, Mauricio Pochettino.

“I think the most important thing for us, is and always will be the health of the player. The game, the result, or that it’s the semifinal of the Champions League, what’s more important is the health of the player. That’s our priority always.

“You can ask the referees. They were in Spanish, talking about the situation. The referee for me was fantastic.

“I want to praise him for his amazing behavior. His priority was the health of the player. He said to me ‘Mauricio, are you sure he’s in a condition to play?’ I said, ‘Ask the doctor, not me’. ‘Doctor is he in a condition to play?’ ‘Yes’, ‘ok, go in.’”

The club added in a later statement on Thursday that Vertonghen had undergone further tests and had seen an independent neurologist, as is standard procedure, and it had been concluded that the defender did not suffer a concussion.

The club said: “The Belgium defender suffered an injury to his nose due to a challenge during the game which resulted in heavy bleeding. He was deemed fit to continue playing after an on-field assessment. All Football Association concussion guidelines were followed.

“Jan was immediately withdrawn as a result of the player informing medical staff that symptoms were developing suddenly and that he no longer felt stable standing up. We have been advised that this was the result of a presyncopal episode, a near faint.”

Vertonghen will not be available to play for Spurs in their Premier League game against Bournemouth on Saturday.

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Jan Vertonghen collided with teammate Toby Alderweireld and Ajax goalkeeper Andre Onana.

Europe’s governing body UEFA, which runs the Champions League, also defended the actions of the officials and Tottenham’s medical staff, saying: “Based on the reports of UEFA’s officials at the match, the concussion procedure was respected during the game, as the referee immediately stopped the match after the incident.

“The doctor was at no point under time pressure from the referee and was given time to make his medical assessment. The stoppage was longer than the three minutes mentioned in the procedure.

“In accordance with the procedure, before letting the player come back onto pitch, the referee went to the touchline to approach the team doctor, who informed the referee that the player is fine to carry on and keep the player on the pitch.”

Football has often been accused of lagging behind other sports in terms of the way that head injuries – and specifically concussions – are treated.

In other sports, the case is different. Since the 2015 Rugby World Cup, teams have been able to make a temporary substitution for any player suffering from a head injury.

In English domestic cricket, temporary substitutions were introduced in 2018. Meanwhile, the NFL – a sport long linked to head injuries – has a “Play Smart. Play Safe.” protocol, with doctors monitoring player welfare on the sidelines using video

If found to be showing any signs of impact seizure or fencing responses – both independent signs of loss of consciousness, the players have to be replaced, according the NFL’s concussion protocols developed alongside the NFLPA.

Former Watford midfielder played for Morocco at the 2018 World Cup while wearing a scrum cap -- just five days after being substituted due to concussion against Iran.

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Yet, in the 2014 FIFA World Cup final, Germany’s Christoph Kramer was allowed to continue after a clash of heads, only to be forced off by concussion later in the game.

“Shortly after the blow, Kramer came to me asking: ‘Ref, is this the final?’” World Cup final referee Nicola Rizzoli later told La Gazzetta dello Sport.

At last year’s World Cup in Russia, Morocco’s Nordin Amrabat suffered concussion during a defeat against Iran, only to play five days later in headgear, which he discarded early on in the match. After Amrabat’s return, Morocco manager Herve Renard described the former Watford player as a “warrior.”

At the time Morocco team doctor Abderazzak El Hifti said he had respected the recommendations of FIFA “point by point.”

Nonetheless the decision went against FIFA’s suggested six-day concussion break. However, the governing body does not have the authority to officially enforce the advice.

“Until FIFA takes its head out of the sand and out of other places, we are going to still be having this conversation,” Twellman added. “If FIFA wants to do something about it and be proactive, then we may be talking about real evolution for the sport and real change.

“If we’re going to be waiting for FIFA, then we’ll be waiting forever.”

In response to CNN’s request for comment, a FIFA spokesperson said: “FIFA regularly monitors the situation of head injuries, maintaining constant contact with current and on-going studies on this matter and reviewing our protocols.

“As mentioned in the concussion module of FIFA’s Emergency Medical Manual, “if, at any stage of the concussion assessment, the medical team cannot make a definite decision regarding whether concussion is present or not and a doubt exists, it is recommended that ‘when in doubt, sit the player out’ and he or she should be removed from play.”