Mats Hummels has slammed Borussia Dortmund's "pathetic" form and has admitted that he is "very concerned" about being relegated this season.
Jurgen Klopp's side lost 2-1 to Werder Bremen on Saturday in a defeat that leaves them joint-bottom of the Bundesliga heading into the winter break.
Club captain Hummels and star man Marco Reus have both been forced to miss segments of the season, and the Germany international admits that injuries to key players have taken their toll.
"It's pretty astonishing that we are so pathetic," he told reporters. "There is no guarantee that it will get better. There just isn't. Almost every key player was injured in the first round [of the season].
"We have played as badly as imaginable. We're very concerned. The way we're playing, we're right down there.
"If we have all the strongest players back by the end of January then it will be different but there's no guarantee of that. Three or four important players could get injured. Then we'll have to deal with it differently from in the first round."
Dortmund, who won back-to-back league titles under Klopp in 2011 and 2012, sit 30 points behind leaders Bayern Munich.
Despite their domestic woes, last season's runners-up coasted through to the last 16 of the Champions League by winning Group D ahead of Arsenal.
