Jan Vertonghen left Tottenham Hotspur in the summer transfer window.

After spending a total of eight years in north London, he moved to Benfica on a free transfer, having made 315 appearances for Spurs.

The centre-back endured a difficult final season at the club, though, making a total of 30 appearances in all competitions, and he only played in one of their final four games of the campaign, sitting on the bench against Arsenal, Leicester City, and Crystal Palace.

Vertonghen, though, has now tried to explain that, and it stretches back to the clash with Ajax the season prior under Mauricio Pochettino.

The 33-year-old clashed heads with his Belgium team-mate Toby Alderweireld in a sickening collision in the first leg in north London.

Vertonghen was initially allowed to play on, after being examined by medics on the sideline, but upon his return, he realised he could not continue and asked to be taken off.

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A ghastly scene played out thereafter, as he almost collapsed in the arms of then-manager Pochettino.

And he has now revealed that he struggled with the after-effects of the injury for around nine months.

He said, per Sporza via Sky Sports: "Many people don't know this, but [the head injury against Ajax] affected me for a really long time. I had dizziness and headaches. The other day, there was the story about David Luiz and [Raul] Jimenez, in which Jimenez suffered a fractured skull.

"With me, it was my nose and I continued to play, which I shouldn't have done, according to the doctors. In the end, I think I suffered from that head injury for about eight or nine months. That was the reason why I didn't play well.

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"I had a year left on my contract and I thought I had to play because I had to showcase myself to other clubs and to Tottenham, but when I played, I was rubbish. I just couldn't produce a good performance. Not many people knew that.

"That was my own choice and not a criticism of anyone else. After five months, there was a day when I started to feel better. When I see the footage from that time, I know when I didn't feel well by looking at myself.

"I think it was in January that I really didn't know what to do. Match after match, training session after training session, there was more impact. Then it was lockdown, so I didn't do anything for two months and after that it was better."

GIVEMESPORT’S Harry Sherlock says…

This is horrible.

And it really doesn’t reflect very well, not just on Spurs, but on football as a whole.

We clearly have a long way to go when it comes to concussion protocols and there should never have been an option for Vertonghen to continue.

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There should have been the option for Spurs to make an immediate substitution – one that did not actually detract from their count of three subs – and protect their player.

That he tried to play on, and could potentially have been exposed to more harm, is a sickening thought.

Football has to do better.