Borussia Dortmund director Hans-Joachim Watzke has spoken of the "crazy group" that pits the Germans against Ajax, Manchester City and Real Madrid in the Champions League.

All four teams in Group D are domestic champions, and while Watzke admitted the group will be tough, he also challenged Dortmund's players to become "heroes".

"In such a group, heroes are born," said Watzke. "This is an incredibly difficult but also incredibly attractive group with three Champions League winners and the English champions.

"We want to progress. This is a crazy group. We could not have drawn any teams harder than Madrid and City.

"Of course it's great to play at the Bernabeu or on English soil, but honestly I would have hoped for an easier draw."

The Champions League group stages begin on September 18.