Zdenek Zeman fired a warning to the rest of Serie A that his side are in a position to challenge those above them as the season progresses.
Jupp Heynckes' side maintained their near-perfect away form with a 2-0 win over Augsburg, ensuring they go into the winter break with just one goal conceded on their travels.
In contrast, the champions lost 3-2 at home to Wolfsburg, leaving them 14 points behind Bayern with Mueller conceding that the next few weeks will be 'boring' for his side.
"As a Dortmund player I wouldn't talk that much about the title anymore. The result (of Dortmund) doesn't make us unhappy," the 23-year-old told Sport1.
"The next few weeks (are going to be) boring. We must not dull ourselves with the big advantage that we have right now."
Meanwhile, team-mate Mario Gomez echoed Muller's sentiments, insisting the title is Bayern's to lose.
"The title won't be decided between Bayern and Dortmund. We can only stop us by leaning back and relaxing," he said.
Heynckes' men encounter Borussia Moenchengladbach next weekend at the Allianz Arena in their final league game of the calendar year.