Tottenham boss Mauricio Pochettino insisted it was the club's medical staff's decision to allow Jan Vertonghen to return to the pitch despite suffering a serious-looking head injury in the Champions League loss to Ajax.
Vertonghen has since been given the all-clear by Spurs, who say he has not suffered a concussion, and walked unaided out of the Tottenham Hotspur Stadium after his side lost the semi-final first leg 1-0.
But the focus will be on how the Belgium defender was allowed back on the pitch, given his poor state when he had to go off again shortly afterwards.
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.
Pochettino had to put his arm around to help keep the groggy defender up, before he was carried away after appearing to retch by the touchline.
A Spurs official told Press Association Sport after the match that Vertonghen was fine and had passed all concussion tests, although the defender will have more assessments over the coming days.
Tottenham boss Pochettino said: "I wasn't involved. I wasn't involved. It was the doctor's decision.
"I think it's so important things, the rules and the protocol are there and our medical staff follow the protocol.
"I was never involved. The decision was the doctor and the referee asked.
"He goes in. In the next action, we need to put him out because he didn't feel well."
Asked about Vertonghen's condition, Pochettino said: "He's OK, he is good, he was walking away. He was more relaxed. I hope it is not a big injury or a big issue.
"I don't know (what the latest is). He was walking away from the stadium now. I hope he is well.
"You know very well you need to keep eyes watching him and analysing him because it was a big knock. But I hope it is not a big issue. At the moment it is OK."
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.
