The worst part about Hoffenheim's opening goal is that Bayern Munich were kind of warned about it. In a "false start" on the kick-off, Hoffenheim players sprinted into the Bayern half of the field. It was a giant BAT SIGNAL screaming, "Hey, guys, we're coming to pressure you the moment you kick that ball."
So, what did David Alaba, Jerome Boateng, and Manuel Neuer do? They fell asleep at the wheel. Alaba's backpass to a back-peddling Boateng was extremely poor, catching the centerback wrong footed. By the time he could recover, Kevin Volland had already jumped in to steal the ball away.
Standing in his penalty area watching all of this unfold in front of him, Neuer rushed out to challenge Volland. The only problem is that Neuer slipped as he started running, so he was scrambling to meet Volland head-on. By the time he got there, Volland nutmegged him for the 1-0 advantage.
This isn't something you're going to see again any time soon. Pep Guardiola will drill these guys into being alert from the opening whistle to not let this happen again.