The 27-year-old Liverpool goalkeeper was again loaned out in the transfer window as Jurgen Klopp decided he had no need for him at Anfield for the current campaign.
Karius has returned to Germany with Union Berlin on loan, but he is fighting to get into the team as Luthe is the number 1 at the club.
He is yet to make his debut for the club and Luthe indicated that he is not feeling threatened by Karius’ presence in the Union Berlin squad.
The 33-year-old custodian has welcomed the competition from the Liverpool loanee and believes that the shot-stopper is only making him a better goalkeeper by threatening to take his place in the team.
Luthe told German magazine Kicker: “I am a fan of maintaining a little competition.
“It doesn’t make me worse when I know Loris is behind me, rather better.”
Karius still has a contract until 2022 with Liverpool and is slated to return to Merseyside again at the end of the season.