While Pierre-Emerick Aubameyang's 75th minute goal wasn't what sent Bayern Munich crashing out of the DFB Pokal, it was nevertheless the Dortmund equalizer that forced extra time. That Bayern Munich eventually capitulated on penalties in embarrassing fashion was just icing on the cake for Dortmund as after the introduction of Henrik Mkhitaryan, they truly bossed the midfield.
Larger than that broad tactical motif though, Aubameyang's goal serves as a highlight of how defensively frail Bayern Munich can be at times. With the play at their front, they're one of the most unstoppable defensive forces in Europe. Turn them around and get them front to goal in any way and they have the propensity to collapse and lose their shape and in that moment they tend to be very vulnerable.
The goal starts with a sequence of play down the right. Dortmund fullback Erik Durm is being pressured by Juan Bernat and Thiago. The Dortmund fullback does an excellent job of hanging onto the ball long enough and creates enough space that he can hit a long pass down the line. Pierre-Emerick Aubameyang's speed becomes extremely critical here as he easily beats Rafinha and Jerome Boateng to the ball. One instant criticism is that Boateng is far removed from the defensive line Bayern have established before the pass is even made. Given the speed of Auabmeyang it's a necessary step to be able to keep the play in front of him but it comes with a cost in that it also opens a channel in the Bayern defense.
The pass into space bypassing both lines of the Bayern Munich midfield is the most dangerous part of this entire play as it takes Thiago's out and leaves Bayern Munich shorthanded in the middle of the park. That ultimately becomes their undoing.
As the play evolves Aubameyang's speed takes him down into the corner as Boateng marks out the opportunity to cross. Rafinha tucks in to assume Boateng's normal position. Meanwhile Marco Reus has made a late run dragging Lahm out of position and leaving Xabi Alonso the lone midfield player poised to cut out the pass back into the center. Aubameyang reads the play, cuts and fires a pass Jakub Blazczykowski before Bayern can respond. The backpass from Aubameyang comes with their commensurate step up from midfield while Alonso moves to pressure Blazczykowski. But with no one in midfield, Bayern Munich have a severe issue.
Unfortunately, the whole thing continues going sideways as Henrik Mkhitaryan drifts off the back shoulder of Mitchell Weiser into a large pocket of open space. Without a midfield defensive structure, Dortmund now have the potential to use three unmarked midfield runners to generate a throughball. This leaves the entire Bayern defense compact to prevent it and comes with the price of leaving the space on the back post. Blazczykowski opts to go over the defense, the time afforded by the out of position central midfield allowing him to perfectly dump the ball into the pocket of open space for Mkhitaryan to run onto.
Mkhhitaryan first times his cross low along the ground and Bayern Munich makes no effort to pursue it -- it seems headed out. But where the speed of Pierre-Emerick Aubameyang was so invaluable in starting this entire sequence for Dortmund, it is once again so vital in ending it. From an extreme angle his spring and sliding finish sees him put it just across the line with a powerful strike that Manuel Neuer is just a millisecond too slow to respond to.
Bayern Munich's initial gameplan on this play was solid and well constructed, but once the defense got turned around and headed at it's own goal, the entire midfield structure fell apart. That lack of structure as they transitioned deep ultimately killed them as it gave Dortmund the space to pick their channels and force the Bayern Munich defense to respond to the most direct and dangerous threats.
That left open lanes that any team could also just as easily exploit provided they have the technical ability to do what Dortmund just did. That's a scary proposition considering Bayern Munich have to face off against Lionel Messi, Luis Suarez and Neymar in just seven days time.