The Magpies’ fourth-choice goalkeeper has been thrust into the spotlight with regular number one Nick Pope suspended following his red card against Liverpool.
Martin Dubravka, who replaced Pope at the weekend, cannot play as he is cup-tied and third-choice Karl Darlow is on loan at Hull.
Here, the PA news agency looks at a challenging four years for the stopper.
Nightmare in Kyiv
Karius is best remembered for two horrendous mistakes in the European showpiece against Real Madrid almost five years ago.
The German gifted Real their opening goal in the 51st minute when he threw the ball out in front of Karim Benzema, who stuck his leg out and diverted it into the net.
Karius was also at fault for Real’s third goal when he let Gareth Bale’s long-range effort slip through his fingers. It later emerged that the goalkeeper was suffering with concussion, possibly following a collision with Sergio Ramos.
After Liverpool broke the world record transfer fee for a goalkeeper by signing Alisson Becker for £66.8million, Karius was loaned out to Turkish side Besiktas.
He spent two seasons there, making 65 appearances, but could not cut out the blunders.
Oh no Loris Karius!
The former Liverpool keeper makes a huge blunder to gift Slovan Bratislava the lead against Besiktas ? pic.twitter.com/t3dUFbQndA
— Football on BT Sport (@btsportfootball) September 19, 2019
Most notably, his misjudged header gifted Slovan Bratislava striker Andraz Sporar the opening goal in a 4-2 Europa League defeat. Karius terminated his contract with Besiktas in 2020 after a pay dispute.
Still on Liverpool’s books but with no prospect of any game time, Karius returned to Germany on loan with Union Berlin.
But he shipped three goals on his debut as his new side were dumped out of the German Cup by second division Paderborn.
Karius went on to make just four more appearances, with his last competitive match coming in a 1-1 draw with Hoffenheim on February 28, 2021.
Karius’ Liverpool contract expired last summer and he was picked up by Newcastle as a free agent in September.
Now 29, Karius has yet to make an appearance for the Magpies but looks set to make his debut in the biggest game in the club’s recent history.
“That was the reason for taking a player of his profile,” said manager Eddie Howe.
“He has experience of the big games, so I’ve got no doubt or issue over his ability to step in.”