Karius has joined Besiktas on a two-season loan.
Orman was critical of current goalkeeper Tolga Zengin's mental toughness after landing Karius.
“Tolga is a competent and good goalkeeper, Orman said. “He has impressive physical attributes however, he allows emotions to cloud his judgement.
“If he makes a mistake during the game he struggles to recover mentally.
“We have to be realistic, for this reason, we decided to sign a new goalkeeper."