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Thiago Alcantara will miss tomorrow's Klassiker between Borussia Dortmund and Bayern Munich.

Bayern manager Hansi Flick confirmed the midfielder will not be available for the game at Signal Iduna Park after being forced to miss his side's Tuesday (AEST) training session.

"Thiago didn't train," Flick said. "Unfortunately, he is ruled out for this game. The final secret regarding the line-up, I'd like to keep to myself."

Thiago has played 23 times in the league this season but sat out the 5-2 win over Eintracht Frankfurt due to a groin problem.

In his absence, Flick hopes to see Leon Goretzka continue his impressive run of form.

"He won plenty of balls against Frankfurt and was very aggressive. That's very important for a holding midfielder," Flick said. 

"He has added some muscle, which has benefited his game. Leon is developing well. 

"He was a little more attacking before, as a 10 or a number eight. But, as a six, he can show off his strength, his sprints forward.

"He interprets things differently to Thiago. I'm happy to have alternatives in this position."

Bayern heads into the game with a four-point lead over Dortmund at the top of the table, with just seven games of the season remaining.

The defending champion is on an eight-match winning run in all competitions and won the reverse fixture 4-0 at the Allianz Arena last November.

The midweek classic takes place just a day after the seventh anniversary of Bayern and Dortmund's meeting in the Champions League final at Wembley in 2013, when Arjen Robben's late goal secured the treble for Jupp Heynckes's side.