The Bundesliga club swooped to snap up Karius from Liverpool on a loan deal in the transfer window and the shot-stopper will be looking to play on a regular basis.
He had to watch Union Berlin’s clash against Schalke from the bench though as Fischer opted instead to play Andreas Luthe in a game that ended 1-1.
Fischer admits that Karius was not happy to learn he would not be playing, but the coach feels the goalkeeper’s reaction was positive as it showed his desire to start.
“Of course, he was not satisfied, hopefully”, Fischer told Sky Deutschland.
“It would be wrong if he just accepted it like that.
“He should show it with his performances and we will see where it goes.”
Karius will be hoping to impress Fischer on the training pitch in advance of Union Berlin’s meeting with Freiburg this coming weekend.
Union Berlin then have another two matches, against Hoffenheim and Arminia Bielefeld, before November’s international break kicks in.
