Dortmund have been Bayern's closest rivals in the past five Bundesliga seasons – winning two titles of their own – but find themselves bottom of the table in the current campaign.
Having lost Robert Lewandowski to Bayern at the end of last season, Dortmund's attempts to replace the Pole's firepower have failed with Ciro Immobile and Adrian Ramos scoring five goals between them so far.
Added to a lack of attacking prowess, Dortmund have also struggled after long-term injuries to the likes of Mats Hummels, Jakub Blaszczykowski, Henrikh Mkhitaryan and Ilkay Gundogan.
They have just four wins from 18 games all season, while Bayern are eight points clear at the top despite their first defeat to Wolfsburg on Friday.
"I like Klopp and Dortmund," said the Spaniard. "They have great players, but now they are bottom.
"We have to watch it [their fall], that could happen to us."
Guardiola is keen to ensure they find their composure again against Schalke on Tuesday despite facing a side the head coach believes are a dangerous opponent.
"If we understand that we can lose tomorrow, then we are on the right track," he added.
"Schalke are one of the best teams in Germany. It is difficult to attack them, we must patiently play.
"They will be super organised defensively."
