Guardiola's side have taken maximum points from their first three league games this season, maintaining a 100% start alongside Borussia Dortmund, Bayer Leverkusen and Mainz.
The Spaniard believes that Bayern will need to be on top form to beat Freiburg this evening, in a match moved forward due to Friday's UEFA Super Cup clash with Chelsea.
He told the club's official website: "We want to continue our run. But they achieved unbelievable things last season.
"Freiburg generate huge pressure when they attack. They are highly capable in the build-up but also very aggressive in defence.
"I know how tough it will be. We'll have to play well, because if we don't, we won't win."
Bayern will be without summer signing Thiago Alcantara for the trip to Freiburg, after the midfielder was ruled out for seven weeks with a torn ankle ligament.