Borussia Dortmund boss Thomas Tuchel has expressed his concern after his side conceded four but scored eight against Legia Warsaw in the Champions League.
The win was a competition record for the number of goals scored in a game andkept Dortmund top of their group with just one game remaining.
But Tuchel was disappointed with the efforts of his defenders, admitting that the issues at the back need to be addressed.
RECORD: Borussia Dortmund and Legia Warsaw have scored the highest number of goals in a single Champions League game (12).
"Apparently there has never been such a thing, so it is also difficult to analyse this game," Tuchel told theclub's official website.
"It was surreal, I have never seen anything like that before. We left so much space in the defence, and we've got a lot of trouble with it.
"Many mistakes were made by us. In the end, we managed to win. I am sorry for Roman Weidenfeller. The blatant mistakes that we have made, I will address."
Tuchel did find a major positive in the return of Marco Reus, however. The German wingerscored a hat-trick in what was his first game since the end of last season.
"It is fantastic that Marco worked so well today. The game was not so intense that I would have to [substitute] him," Tuchel added.
"He has recently been training at a very high level, but we could not expect him to score three in his first game back, especially in the Champions League and without competitive action under his belt.
"We had to wait a long time, much too long. It was an amazing comeback from him."