Bayern are expected to stroll into the semi-finals when they host Heidenheim on Wednesday evening, just three days before their key Bundesliga meeting with title rivals Borussia Dortmund.

Yet Hummels, who follows the second tier club closely, said Bayern should not get ahead of themselves in what could be a season-defining week.

"We have to be 100 percent focused against Heidenheim because they won't be a pushover," he said on Tuesday.

"A good friend of mine is a big Heidenheim fan, so I watch them quite a lot. They play good football, particularly going forward."

Heidenheim are currently sixth in the German second division Bundesliga 2, and have punched above their weight in recent seasons. They reached the German Cup quarter-finals thanks to a shock victory over Bayer Leverkusen in the previous round.

Hummels reserved particular praise for the "powerful headers" of striker Robert Glatzel, who has been linked with a move to several Bundesliga clubs.

He insisted that Bayern need to stay cool if they are to stay on course for a domestic double this season.

"If we were only thinking about the Dortmund game on Saturday, then we would be fired up," he said.

"But first it is all about the cup. We obviously want to get into the semi-finals, because winning the cup is one of the two major aims we have this season."