If the Euro was abandoned each country would have to go back to it's own currency.
Germany is so much stronger than the others that the DM would have such a high exchange rate in comparison to the other European currencies and the US Dollar, UK pound etc. that their exports would suffer horribly.
Spain, Italy, Greece etc. would have such shit exchange rates they would not be able to import anything from the far east or other countries especially Germany.
This is the reason why Germany is so keen to keep the Euro at all costs. To go back to the DM would spell economic disaster for Germany.
I watched this being spelled out on a BBC tv show about the future of the Euro last year around the time the Greeks were being bailed out again.