Die Roten ran away with the German title last season and the former Arsenal goalkeeper believes things could be even more one-sided under the Spaniard next term
The Bavarians romped to an historic treble last term, claiming the Champions League and DFB-Pokal after winning the league with a record six rounds remaining.
Lehmann feels that next year's German title race could be even more straightforward for die Roten, in light of the arrival of former Barcelona boss Guardiola as well as playmaker Mario Gotze from Bayern's closest rivals, Borussia Dortmund.
"The 'Boredom League' will be rather one-sided in the upcoming season," the former Germany international is quoted as saying by Bild.
"Guardiola will take his place in the Bundesliga in conditions similar to those he enjoyed in Spain.
"[Bayern and Barcelona] are two financially very, very successful teams. The rest are so far behind. No challenge will come from elsewhere [for Bayern].
"The only challenge will come in the Champions League, or maybe the Club World Cup."
Guardiola won three successive Liga titles in his four-year stay at Camp Nou, as well as two Champions Leagues, before taking a year-long sabbatical from the game last season.