Bayern Munich face a nervous wait to find out the extent of centre-back Jerome Boateng's groin injury as the German champions struggle with a defensive injury crisis.

The 27-year-old Germany international had to be helped off in the second-half of Bayern's 2-1 win at Hamburg on Friday, when the German league resumed following its winter break, and he is doubtful for next Saturday's game at home to bottom side Hoffenheim.

A more detailed examination will take place in Munich over the weekend, but another long-term injury would leave Bayern short at the back, with centre-back Medhi Benatia and wing-backs Juan Bernat and Rafinha all sidelined.

"We have a problem, but we'll find a solution," said coach Pep Guardiola.

Boateng is rated doubtful for the Hoffenheim clash, but Bayern have a month to recoup playing resources ahead of their Champions League last 16 tie against Juventus.

"Things are slowly getting a bit tight in defence and it's important that we get a few injured people back soon," said captain Philipp Lahm.

"I don't have an explanation as to why we are picking up so many injuries all of a sudden.

"I'm not an expert."

Meanwhile, Bayern left mid-table Hamburg with three points thanks to two goals from Poland striker Robert Lewandowski, to move 11 points clear in the league table ahead of Saturday's fixtures.

"We knew we'd get nothing for free here," said Thomas Mueller, who played a big part in both Lewandowski's goals.

"Several other teams had difficulties against Hamburg too.

"We know we're not yet in top form, but I'm happy. We aim to improve with every match."

After Lewandowski netted a first-half penalty, Hamburg equalised with a free-kick from Aaron Hunt before the Poland striker netted his second after flicking in Mueller's shot.

"In the first half we controlled the game, but we were asleep when Hamburg had their free-kick," said Lewandowski, scorer of 17 goals in 17 league games this season.

"Fortunately we've still won and we know we still need some time after the winter break.

"The main thing was to take three points in the first match of the year."