Mats Hummels launched a remarkable attack on his own team after branding Borussia Dortmund's form so far this season as "pathetic".
The 26-year-old centre-back, who captains the Bundesliga side, sees his team second-bottom in Germany's top flight at the midway point of the season.
Dortmund lost to Werder Bremen, who had been bottom before the victory, on Saturday to leave them with just 15 points from 17 matches as they head into the six-week winter break.
Hummels remains Manchester United's top January target with speculation mounting in recent weeks. Some reports suggest United could pay more than £40million for the World Cup winner.
The Dortmund captain has previously stated he is happy to stay at the club but his latest outburst will raise concerns that he is attempting to force an exit from the club.
"We’ve managed pretty well at home in recent weeks, but not at all away," he ssaid on Sunday night. "It’s pretty astonishing that we are so pathetic."
Dortmund finished comfortably as group winners, ahead of Arsenal, in the Champions League drawing Italian champions Juventus in the last-16.
Speaking after the defeat on Sunday, Dortmund manager Jurgen Klopp said: "I wouldn't write us off. We made too many mistakes and now we're there like idiots in the relegation zone.
"But we're not as bad as that. We have time now to recharge the batteries. We'll correct what we've messed up."
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