Loris Karius sustained a concussion during the 2018 Champions League final.

The lesser-spotted Liverpool goalkeeper revealed as such on the back of producing an infamous performance against Real Madrid where his errors allowed Karim Benzema and Gareth Bale to score.

According to a translation by Goal, Karius explained in a 2020 interview with Sport Bild: “I had a concussion after a blow from Sergio Ramos, which restricted my spatial vision. 

Karius revealed he had concussion

“This was unequivocally ascertained in a detailed study by one of the world’s leading brain specialists.

“At first, I was happy to know what went on in this game. I didn’t want to make it public myself. When the result was released, there was a lot of malice and insult, often well below the belt.

“I never used it as an excuse. But when people make fun of someone who has badly injured their head, I have no understanding.”

The German shot-stopper had received a blow to the head during an incident with Ramos, who had already sparked controversy earlier in the game after causing Mohamed Salah's shoulder injury.

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Karius' concussion diagnosis

And according to the Daily Mail, Massachusetts General Hospital confirmed Karius' concussion - which took place before Real's goal - with an official statement having run medical tests.

“With Mr Karius’s permission, we are providing information about his medical situation in an effort to prevent, where possible, the dissemination of incomplete or erroneous information," the hospital explained.

“After carefully reviewing game film and integrating a detailed history, physical examination and objective metrics, we have concluded that Mr Karius sustained a concussion during the match."

Why is it so often forgotten?

Now, while you would think that would be something definitive and clearcut, it's remarkable how Karius' concussion is so often swept under the carpet when people think back to that night in Kiev.

You only have to look at the fact that Jurgen Klopp felt the need to substantiate his own reference to it during a press conference before Liverpool and Real meet again in the 2022 Champions League final to get that very point.

Per the Evening Standard, Klopp reflected on the infamous final of four years ago by saying: “Karius had a concussion. It was proven afterwards. Nobody talks about that."

It really is head-scratching that what could well be considered as the proven cause behind one of the most talked about and maligned goalkeeping performances in history has become something of a footnote in the history books.

But perhaps that's got something to do with the reaction to Karius' diagnosis at the time with certain fans and even players casting doubt on whether or not the Ramos clash influenced his errors.

Soccer Football - Champions League Final - Real Madrid v Liverpool - NSC Olympic Stadium, Kiev, Ukraine - May 26, 2018 Liverpool's Loris Karius reacts after conceding their first goal scored by Real Madrid's Karim Benzema REUTERS/Kai Pfaffenbach

Kroos' reaction to Karius' concussion

And of all the fellow professionals to give their two cents on the matter, few pulled their punches quite like Toni Kroos, who found himself on the winning side with Real Madrid on that night in Kiev.

The Los Blancos midfielder has never been afraid to put his cards on the table and dish out opinions that not everybody likes, which was exactly the case when he was quizzed on Karius' concussion diagnosis.

According to Sport Witness' translation, the World Cup winner was quoted by Bild in 2018 as saying: “I don’t know if that explains the errors – I don’t really see it that way.

"If it’s a concussion and you notice it so extreme, I don’t know if you can or should continue playing. If it’s a concussion, it cannot have been so serious. He also had the opportunity to keep the ball in his hands.”

Soccer Football - Champions League Final - Real Madrid v Liverpool - NSC Olympic Stadium, Kiev, Ukraine - May 26, 2018 Real Madrid's Toni Kroos celebrates winning the Champions League at the end of the match REUTERS/Hannah McKay

Oof. That's got to hurt.

Did the concussion cause Karius' errors?

The medical evidence and statements seem to make it very clear that Karius did indeed have concussion, which Kroos doesn't dispute, but what does that mean for the infamous mistakes?

Well, truth be told, that's only a question that Karius himself can answer as he played on after the collision with Ramos to later throw the ball to Benzema and let Bale's strike slip through his fingers.

However, no matter which school of the thought you belong to, the reality of the situation is that Karius made the mistakes that he did and Kroos got his hands on the Champions League trophy.

Liverpool are TOO GOOD for Real Madrid! (Football Terrace)

But you can bet your bottom dollar that it will serve as an extra ounce of motivation as Liverpool look to exact revenge on Real when they lock horns at the Stade de France later