Bayern Munich's injury crisis in defence has worsened with Javi Martinez ruled out of Sunday's Bundesliga match against Hoffenheim and set to miss the coming weeks.

Bayern's director of sport Matthias Sammer confirmed reports Martinez has injured his left knee, the same joint in which he tore the cruciate ligament in August 2014, but played it down.

"It's not a big story," he told German Sky, as Bayern played a three-man defence against Hoffenheim in Munich.

"He has a problem and accordingly, our doctors have taken various measures and he'll be examined again."

Martinez is the 15th Bayern player to have picked up an injury this season, but he took to Twitter to say it "isn't serious" and he hopes to be back "soon".

With Germany defender Jerome Boateng already missing with a groin injury, it leaves Bayern coach Pep Guardiola with just one fully-fit centre-back in Holger Badstuber.

Medhi Benatia is on his way back from injury, while wing-back Rafinha is recovering from a bruised knee.

There are just over three weeks before Bayern play last season's finalists Juventus away in the last 16, first leg, of the Champions League with the return match in Munich on March 16.

On Friday, Bayern chairman Karl-Heinz Rummenigge insisted the club will not bring in any new defenders with the January transfer window to close at 1800 local time (1700 GMT) on Monday.

Sammer echoed his boss, saying: "One must always be attentive, but our team is well stocked. I can't imagine that we'll do anything."