Borussia Dortmund general manager Michael Zorc admits his side have put their Champions League qualification hopes in doubt with their form in the first half of the season.
Dortmund currently sit in fourth in the Bundesliga table at the midway point of the season, 12 points adrift of leaders Bayern Munich, and have already suffered five defeats, most recently at home to Hertha Berlin.
Zorc has called on the players to give their all in the second half of the campaign or risk losing out on a return to the Champions League next season.
"We are lagging a bit behind our own expectations in the Bundesliga," he told Bild.
"Of course [missing out on Champions League qualification] is a risk. To achieve our goal for the season is a tough job. We need an extremely strong second half."
Zorc stressed he was nonetheless pleased with BVB's performance in their tough Champions League group stage and pointed to the return from injury of the likes of Ilkay Gundogan and Marcel Schmelzer as cause for optimism after the winter break.
"In the Champions League we not only established ourselves in a tough group, but we came first. That was a great performance," he said.
"We have players who are coming back from injury. Gundogan and Schmelzer trained with the team before the Hertha game. It's convenient for us that our injured guys can now join the team preparation."