Since returning in late January, Bayern have lost to Wolfsburg, drawn with Schalke and beaten Stuttgart, ahead of Saturday's clash with traditional rivals Hamburg.
Guardiola was critical of their performances in all three games, with only the second half against Stuttgart meeting his high expectations of the runaway leaders.
The recent run of results has seen their lead cut to eight points and the Spaniard has warned they must improve quickly if they are to defend their title this season,
"I know that if we play like in those three games, we will find it difficult to defend our title in the Bundesliga," he said. "And we will have no chance in the Champions League.
"But I also know that we will improve. For sure!
"Our building game was very slow in the first half in Stuttgart. I hope it's better tomorrow. We talked about it and trained."
