David Wagner believes psychological problems are to blame for Schalke's sluggish return to Bundesliga action, while Suat Serdar is facing another spell on the sidelines.
After falling to a resounding 4-0 defeat to Borussia Dortmund in the Revierderby last weekend, Schalke went down 3-0 at home to Augsburg on Sunday.
Eduard Lowen's magnificent free-kick put Heiko Herrlich's side in front after six minutes and Noah Sarenren Bazee doubled its advantage in the second half, punishing some lacklustre defending from Salif Sane and Jonjoe Kenny.
Levent Mercan was caught in possession by Augsburg substitute Sergio Cordova in injury time and the striker rounded Markus Schubert to complete the scoring.
Schalke sits eighth in the Bundesliga, 16 points adrift of the top four with nine games remaining, with the pressure mounting on Wagner.
"The game started badly. We weren't dangerous enough with all the possession we had," said Wagner.
"We were really tense in the second half. Conceding goals from individual errors is typical of the situation we find ourselves in right now.
"Now we need to support the lads so they start playing with confidence again. We are making too many individual errors leading to goals. A lot of it is psychological."
Serdar last week made his return from a broken toe sustained before the Bundesliga was suspended due to the coronavirus pandemic.
The Germany international suffered another injury early in the second half and had to be replaced by Ahmed Kutucu in the 56th minute.
Wagner explained: "He suffered an injury to the head of his fibula. I can't say right now how serious it is. He is undergoing scans at the moment."