Bayern Munich's Arjen Robben (Photo: Reuters)
Heynckes told reporters midfielder Bastian Schweinsteiger, rested in Wednesday's 2-0 win at Freiburg to avoid a booking that could have ruled him out of the derby, would be back in the squad for Saturday's game.
"(Robben) still needs to get fit," Heynckes told a news conference. "It is understood that Bastian will be back in the squad."
Dutch international Robben has been dogged by a string of injuries again this season but his team has surged to a 10-point lead at the top with 12 wins in 14 matches for the best start of the Bundesliga's 50-year history.
"My aim is for us to extend our lead at the top of the table. It is a prestige duel between the league's top two teams," Heynckes said. "I hope my team is aware that it needs to come up with an above-average performance tomorrow."
Saturday's clash against third-placed Dortmund, 11 points adrift, is not only vital in Bayern's bid to end a two-season silverware drought.
They are also eager to snap Dortmund's five-match winning streak against them as they clinched back-to-back league titles and a German Cup last season with a 5-2 demolition of Bayern.
"This time we have a jaw again," Heynckes said. "Last year my grandmother did not have teeth. This year she has a denture and can bite again," he said, using a curious example, much to the amusement of attending journalists .
Defeat to Bayern would all but end Dortmund's title hopes leaving them 14 points adrift.
Both teams have also qualified for the Champions League knockout stage.
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