The 46-year-old believes his side did not have a lucky break in the 2-1 loss at Wolfsburg, which saw Ivica Olic claim all three points with a wonderful finish
The Ruhr giants slumped to their second defeat this week thanks to an Ivica Olic wonder-strike in a match which saw Neven Subotic stretchered off with a serious-looking injury.
With Bayern Munich winning 3-0 against Augsburg - a Bundesliga record - Dortmund fell further behind in the title race with this loss, and the 46-year-old believes that fortune abandoned his troops in every 50-50 situation in the match.
"It was a tight game," he is quoted as saying by the club's official website.
"During the first half, we had some, but too few, good moments. We often built well, but made it too easy for the opponent.
"Nevertheless, we scored a great free kick for the first goal and came out of the dressing-room well and were really in the game, with the second goal coming.
"But then [Ricardo] Rodriguez came with a great free kick and Olic scored a wonder-goal. We tried everything, but everything went against us in tight situations."
Initial reports have suggested that Subotic has torn his anterior cruciate ligament.