"He cost £4 million from Mainz and he is going to be immense."
One very much doubts it now. Not after this. Not after two of the worst goalkeeping mistakes ever seen at the highest level.
As Karius lay on the turf at the full-time whistle, his shirt pulled over his head, it was impossible not to wonder how on earth he will recover from deciding the biggest game of his life in Real Madrid's favour.
He effectively threw the ball into his own net twice, first via the outstretched boot of Karim Benzema, the second time by somehow failing to deal with Gareth Bale’s speculative shot from distance.
As former Germany No.1 Oliver Kahn told ZDF , "I'm lost of words. I can't remember to have experienced something more brutal from a goalkeeping point of view than in this final. An evening like this can destroy a career."
Certainly, this was a goalkeeping calamity on an unprecedented scale, on the club game's grandest stage.
Brazil goalkeeper Moacir Barbosa was blamed for his nation's shock loss to Uruguay in the deciding game at the 1950 World Cup in Rio, as he had arguably been beaten too easily by Alcides Ghiggia's winning goal. But it was nothing compared to Karius' clangers in Kiev.
The Brazilian press needed a scapegoat for the national embarrassment and they turned on Barbosa. It was a pain that he carried with him for the rest of his days. Selecao forward Zizinho even blamed the press for his death some 50 years later.
The sporting world will hopefully be kinder to Karius as it was difficult not to be moved by his attempts to apologise to Liverpool's supporters for his two atrocious errors.
But there was no denying that it was Karius - not two-goal hero Bale - who had proved the difference between the two sides.
"They've been done by two individual mistakes," former Liverpool captain Steven Gerrard told BT Sport . "The talking points will be the goalkeeper mistakes."
That is unavoidable. Karius' errors were so bad, so basic, so inexplicably absurd, that they actually managed to overshadow one of the greatest final goals in football history, from Gareth Bale.
Frank Lampard said, "Those mistakes shouldn't be happening in Champions League finals." He wasn't wrong. Such mistakes shouldn't even be happening at Sunday League level. This was no way to lose.
"On a human level you can feel sadness for Loris Karius," Lampard added. "That's with him for life now. The first one, which kind of changed the momentum of the game, I couldn't believe what I was seeing.
"It's a horrible moment for him. he needs some big support from his team-mates now. He didn’t mean that but it’s cost them the game."
It was a harsh but fair appraisal. Even worse, while the manner of the mistakes was shocking, there was nothing remotely surprising about the fact that it was Karius who cost Liverpool a sixth European Cup.
His form, as Grobbelaar pointed out, has improved since the arrival of the aerially dominant Van Dijk at Anfield in January, and since being installed as Liverpool's No.1 on a regular basis.
But he has never instilled confidence in his defence, in his club's supporters. He has always looked liable to make mistakes.
Even Klopp knows this, even if he hasn't admitted it publicly. Why else were Liverpool so enthusiastically pursuing Roma's excellent goalkeeper, Alisson, only to be put off by the price?
Unfortunately for the Reds, Klopp's show of faith in Karius has now proven an incredibly costly error of judgement.
The hope is that the 24-year-old gets the emotional and mental support he needs to recover from this shocking setback.
He deserves sympathy. Sadly, though, he doesn't deserve to be a starting goalkeeper for a side with Champions League aspirations. Liverpool want to win major trophies and that is impossible without a top-quality goalkeeper.
That was proven beyond all doubt in the most traumatic and costly of circumstances in Kiev on Saturday night.
Liverpool’s anthem is ‘ You’ll Never Walk Alone ’ and Karius will need the help of his team-mates, his coaches and his club’s fans to help him get through the coming days, weeks and months of what is likely to be the darkest period of his career.
But the cold hard reality is that Karius is not good enough for Liverpool, and arguably never has been.