Captain Mats Hummels has urged Bundesliga strugglers Borussia Dortmund to stop wasting their potential.
Dortmund have provided the most consistent challenge to the domestic dominance of Bayern Munich in recent seasons.
However, Jurgen Klopp's men have failed to reach their usually lofty standards in the 2014-15 term and they headed into the mid-season break languishing in the relegation zone.
Centre-back Hummels believes that Dortmund were scarcely outplayed in the first half of the campaign and their problems were mental.
The Germany international is now desperate for the side to start living up to their billing as one of Europe's best teams.
"The only thing I want is for us to stop wasting our potential," he told Der Welt am Sonntag.
"We have fought in every game, it was rare that an opponent was better than us. It became a mental problem."
Hummels has been consistently linked with an exit from Signal Iduna Park with Premier League duo Manchester United and Arsenal both thought to be interested in the World Cup winner.
Reports suggest that Hummels may seek a move with Dortmund struggling to contest next season's UEFA Champions League, but he insists it is not imperative he plays in Europe's premier competition.
"As a general rule I don't have to play in the Champions League to be happy," he added.
"In 2008 when I came Dortmund [on loan from Bayern Munich] the Champions League was far away. In 2009 when I decided to stay permanently, that [the Champions League] was not the decisive reason for staying."
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