The Bundesliga side swooped to land Karius on loan from Liverpool in the transfer window and the shot-stopper is battling Luthe for the number 1 spot at the Stadion An der Alten Forsterei.
Luthe started in Union Berlin’s 1-1 Bundesliga draw with Schalke on Sunday, with Liverpool loanee Karius sitting on the bench.
Karius was praised post match by Luthe, with the goalkeeper tipping his hat to the Liverpool man.
“I appreciate him as a goalkeeper”, Luthe said on Sky Deutschland after the final whistle.
“He is a very, very good team-mate”, he added.
Luthe is expected to battle Karius for the number 1 spot at Union Berlin and he believes that it is good for the club that there is competition for the place between the sticks.
“In the Bundesliga, it is generally about having the best squad”, the 33-year-old explained.
“We certainly have that in the goalkeeping position.”
Union Berlin managed to finish in eleventh in the Bundesliga last term, steering clear of the drop zone by a comfortable ten points.