The defender says the national side must improve at the back if it is to lift the World Cup in Brazil next summer.
Joachim Low's side has shipped nine goals in its last three internationals and let a 4-0 lead slip at home to Sweden last October, with the game ending 4-4.
"The players and coaches have come together to discuss the basic principles of our defense," Mertesacker told dfb.de. "We've been playing a different system so we need to learn the philosophy for this shape. We need to know when to drop back, when to move out, how to deal with certain situations and how to protect one another."
Germany takes on Austria at the Allianz Arena in Group C on Friday night, and Mertesacker is hoping for a collective team effort in becoming a more resolute defensive unit.
"Goals often come from a mistake much further up the field, yet the analysis and blame will always be on the defense," Mertesacker said. "We cannot take responsibility for every goal we concede, we all need to do our part across the field to ensure we win as a team."
Germany currently leads Austria by five points at the top of its group with five wins from the six qualifiers to date.