Dortmund coach Jurgen Klopp has called on his team to become more clinical in front of goal, after overseeing a tight 1-0 win over Werder Bremen on Saturday.
Shinji Kagawa's strike early in the first-half was enough to bag all three points for the German champions' but, according to the 44-year-old, they were fortunate to get away with their lack of application in their opponents' box during the encounter.
"I can only criticise our failure to finish off our opportunities," Klopp told the press after the game.
"We left the game open for too long, so it could have made for an uncertain ending to our performance. Still, I am very pleased we were extremely lively."
Dortmund remain five points clear of nearest challengers Bayern Munich at the league summit, after the Bavarians cruised to a 6-0 victory over Hertha Berlin.