Guardiola also said that it might take a while for his team to get back into the rhythm as the majority have spent the last week on international duty.
"Mainz have been able to focus on the game for ten days," Guardiola told Bundesliga.com. "We just had our first training session today.
"They can play to various systems, are very hard-running and well-organised at the back."
Bayern currently top the table by one point from Borussia Dortmund.