A handful of mainly U.S.-based macro hedge funds have led bets against China's yuan since late last year and the coming weeks should tell how right they are in predicting a devaluation of between 20 and 50 percent.
Since at least last September, Texas-based Corriente Partners, which made hundreds of millions of dollars foreseeing Europe's debt crisis, has been accumulating tailored "low delta" options - essentially bets with long odds - that provide for an up to 50 percent fall in the yuan.
The firm reckons rush by domestic savers and businesses to withdraw money from China will prove too strong for authorities to resist and control, even with $3.3 trillion in FX reserves, the biggest ever accumulated.
London-based Omni Macro Fund has been betting against the yuan since the start of 2014.
Several London-based traders said U.S. funds, including the $4.6 billion Moore Capital Macro Fund, have also swung behind the move.
Data from Citi, meanwhile, shows leveraged funds have taken money off the table since offshore rates hit 6.76 yuan per dollar three weeks ago.
Many players say that whether outflows resume in earnest after the Chinese New Year break in the second week of February should show whether funds are right to expect more dramatic declines.