Bank stocks, when the stock market opens, will also be hit with a selling wave, as they cannot survive if the European Central Bank withdraws its emergency lending program.

There are not as many hedge funds in Greece as there were a year ago, when it is estimated that around 100 foreign funds were sitting on big investment stakes. Their bet was that the previous Greek government would be able to complete the arduous process of economic reform in Greece that started five years ago.

Image David Einhorn is among the hedge fund investors who have collectively poured more than 10 billion euros into Greek bond, bank stocks and other investments. Credit... Mike Segar/Reuters

When it became clear that a radical Syriza government under Mr. Tsipras would come to power, many investors quickly turned heel, dumping their Greek government bonds and bank stocks in large numbers before and after the election.

But a brave, hardy few stayed put — around 40 to 50, local brokers estimate — taking the view that while the new left-wing government could hardly be described as investor friendly, it would ultimately agree to a deal with Europe. It would be a bumpy ride for sure, but for those taking the long view that Greece would remain in the eurozone, holding on to their investments as opposed to selling them in a panic seemed the better course of action.

For now, at least, that seems to be a terrible misjudgment, especially if Greece defaults and leaves the euro.

Most of the hedge fund money in Greece is invested in about 30 billion euros of freshly minted Greek government debt securities that emerged from the 2012 restructuring of private sector bonds.