Vertonghen was forced off the pitch in the first half of Spurs’ Champions League semi-final first leg against the Dutch giants following a clash of heads with Alderweireld.
The Belgium international headed the back of his team-mate’s head shortly after the half-hour mark whilst trying to get on the end of a free kick.
The 32-year-old immediately collapsed to the floor and his nose soon began to pour with blood.
Tottenham medical staff immediately rushed to his aid and appeared to have patched him back up for duty after five minutes of treatment.
But seconds after returning to the pitch, the Belgian began exhibiting signs of concussion as he lost his balance and began to feel nauseous.
Spurs doctors raced back to his aid and helped carry him back to the treatment room.
Pochettino, who also helped usher the former Ajax man off the pitch, shed some light on his condition after the match.
And he revealed he’s currently in the dark over the veteran defender’s condition.
Jan Vertonghen suffered a sickening injury against Ajax (Image: GETTY)
Jan Vertonghen clashed head with Toby Alderweireld (Image: GETTY)
“I don’t know I didn’t see him,” Pochettino said in his post-match interview. “Of course we’re going to assess [him] in the next few days and we’ll see.”
BT Sport present and former Tottenham hitman Gary Lineker was greatly worried by Vertonghen’s injury and voiced his concern during the half-time interval.
He said: “Jan Vertonghen, a bit concerning how he reacted when he went back on the field of play and then came off.
“He seemed fine there and then he kind of lost his legs and everything. Whether he kind of fainted. He’s okay in the dressing room apparently.”
Jan Vertonghen grabs his nose shortly after the clash of heads (Image: GETTY)
We’re going to assess [him] in the next few days and we’ll see.
Vertonghen’s concussion capped off a night to forget for Tottenham, who suffered a 1-0 defeat to Erik ten Hag’s side.
A first-half strike from Donny van de Beek sealed victory for the Dutch powerhouses, who were 150/1 to win the tournament a few months ago.
Tottenham offered very little going forward and were clearly feeling the effects of their depleted squad with Harry Kane injured and Heung-min Son suspended.
“We were under-par, we didn’t play our best at all,” said Spurs midfielder Christian Eriksen.
Jan Vertonghen receives treatment from Tottenham’s medical team (Image: GETTY)
“In the first 20 minutes, we were ball-watchers. We need to change it up a lot for the next game.
“We made them look a lot better. They are a good side, but we helped them along the way. It was our fault. We were better in the second half.
“At the start, the system didn’t matter. The change gave us a different way to press, to play more direct. But we were still far from where we know we can be.
“No one wanted to play the first half we did. Everyone knew we didn’t compete. We still lost, but we were better in the second half.
Donny Van Der Beek scored Ajax’s crucial away goal against Spurs (Image: GETTY)
“We can’t keep talking about injured players. In a semi-final it doesn’t matter who plays, we have to step up. We’re lucky they hit the post and hopefully, we can turns things around in Amsterdam.”
Ajax’s win at the Tottenham Hotspur Stadium was their third major scalp away from home in Europe this season.
Ten Hag’s men went into the match having already eliminated Spanish and Italian giants Real Madrid and Juventus from the competition and are on course to do the same to Spurs.
BT Sport pundit Rio Ferdinand was blown away by their performance, saying: “It was professional and mature from Ajax.
Mauricio Pochettino’s men have it all to do next week in Amsterdam (Image: GETTY)
“In the first half they played fantastic football. In Spurs defence, if you take 44 goals out of the side in Harry Kane and Son Heung-min, any team would suffer.
“I do think they are still in it. Their away form in this tournament shows they are capable of getting a result.”
Tottenham have it all to do in next week’s second leg at the Amsterdam Arena on Wednesday (8pm).
They will, however, be able to call on the services of Son who will return from suspension.
