Liverpool goalkeeper Loris Karius has suffered an injury setback with loan club Union Berlin.
It's a blow for Karius in a week which also saw Union's No1 Jakob Busk break down with injury.
"Karius was injured in training on Wednesday and had to retire," said Union coach Urs Fischer.
"Busk could not train on Thursday either, and it is very doubtful whether they are available for us."
Karius has begun the season behind Busk.
