Werder Bremen defender Mikael Silvestre will be sidelined for several months after suffering a knee injury.
The former Manchester United man will undergo a knee arthroscopy on Monday, adding to Bremen's defensive woes.
Injuries to Per Mertesacker and Naldo have already left the Germans short at the back ahead of their pre-season campaign.
General manager Klaus Allofs is actively seeking cover, with Nurnberg captain Andreas Wolf heading his list.
Alloffs said: "We are unable to foresee things with regards to the defence.
"We have been looking into the signature of Andreas Wolf, but still nothing is signed just yet.
"He is a good player with plenty of Bundesliga experience and he is available on a Bosman, this is making him very interesting for a club like us.
"Anyway, there are some other options we are also considering for a deal."