Borussia Dortmund were dealt a double injury blow for Saturday's key Bundesliga showdown against Bayern Munich with both defenders Mats Hummels and Marcel Schmelzer ruled out with injury.

The pair limped out of Germany's 1-0 friendly win over England on Tuesday and scans revealed centre-back Hummels is out until 2014 with a torn ligament in his right ankle, while left-back Schmelzer is out for three weeks with a torn left calf.

"Bad news for me today. I won't be able to play any more this year so all I can do is support the guys in the next weeks," Hummels wrote on his Facebook page.

"It will be very difficult, but I am optimistic we can make it through these games."

The timing is bad for Dortmund, who must beat Napoli at home in the Champions League next Tuesday, then Marseille away on December 11, to keep alive their dreams of reaching the knock-out stages.

With Hummels' centre-back partner Neven Subotic out for six months with torn knee ligaments and right-back Lukasz Piszczek only just back from surgery, it means Dortmund are without their first-choice back four against the European champions.

Subotic's possible replacement, ex-Germany defender Manuel Friedrich, 34, who was released by Bayer Leverkusen at the end of last season, picked up an injury in a practice match on trial with Dortmund on Tuesday, according to German daily Bild.

Having come on as a second-half replacement at Wembley, Hummels lasted just 20 minutes on Tuesday while Schmelzer played the first-half against England and was taken off at half-time.

With European champions Bayern four points clear in the league, Munich coach Pep Guardiola was also presented with an injury concern from the England-Germany match as centre-back Jerome Boateng was also taken off after halftime with a minor heel injury.