But Virgil van Dijk has drastically improved the Merseyside club's defence after his £75m arrival from Southampton last month, according to the ex-Reds right-back.
There was a switch at the turn of the year, when Karius played in the league and Mignolet had the two FA Cup ties against Everton and West Brom but there will not be a switch in Portugal.
LORIS KARIUS is on a mission to prove he is Liverpool's No1 - by catching everything in sight.
Liverpool are in a virtually unassailable position heading into the second leg at Anfield, and Klopp will not only be delighted that his vaunted attack of Firmino, Mane and Salah ran riot at the Estadio do Dragao, but also that his side kept a clean sheet. "I'm feeling good, I'm feeling strong and getting consistent game-time helps a lot".
"Virgil has played quite a bit now and we're getting more used to each other - that's important for the team", Karius told the Liverpool Echo.
"Of course he has to adapt a bit because our style is so different". I have to make a decision for tomorrow night. We defend high. He needs to get used to Dejan [Lovren] and Joel [Matip]. "I enjoy every day of being here as it's a great club".
"Nobody knows about the future, or I don't know about the future", Klopp said in his press conference, per the Daily Mail. I know Klopp changed and put Lovren against Porto. "But I haven't made the decision so far".