Borussia Dortmund manager Jurgen Klopp is looking to bolster his defenisve ranks after the long-term injury to Neven Subotic.
Serbia international defender Subotic's season appears to be over after he tore cruciate knee ligaments during Saturday's 2-1 loss at Wolfsburg.
Klopp believes it is too early to throw Germany youth internationals Koray Gunter and Marian Sarr into the deep end.
Instead, a possible option could be unattached former Germany international Manuel Friedrich, who is currently on trial at the club. Klopp knows the 34-year-old defender from a spell both had at Bundesliga outfit FSV Mainz 05 in the past.
The Borussia Dortmund boss told Deutsche Presseagentur: "Of course, we have those youngsters like Koray Gunter and Marian Sarr. But you have to keep in mind perfect youth development needs the right moment.
"Gunter has had injuries and featured in just 28 minutes of action in October. And for Sarr, who could still feature with the U19, the current time would also not be the perfect moment to be thrown in at the deep end.
"This is why we have to look forward to find workarounds."