The only formation that comes to mind considering Kehl is injured and Da Silva a sub would be a 4-1-4-1:
-------Roman-----------
Pisczek-Hummels-Subotic-Schmelle
-----------Bender-------------
Kuba---Götze---Kagawa---Großkreutz/Gündogan
-----------Lucas-------------

But Klopp hasn't changed his 4-2-3-1 since he arrived, doubt he will change it....
Against Paris Götze played alongside Sahin in the Defensive midfield because Bender couldn't play.... Maybe over the summer that will be the training, for Götze to take Nuri's spot....
We'll see

I guess he will not be replaceable.... I find it much more likely to see a change in formation than finding a replacement. Right now, I am also still too disappointed to think of any solutions. Kloppo and Zorc know what they are doing!

So guys, now that it's official I wanted to know who might replace him.
If you hear any news regarding possible replacements then post them---> HERE!
Cheers