At 0700 GMT the rand was 0.5% weaker at 15.5350 per dollar, it softest level since Friday, and a touch above the 15.50 technical level that could trigger more selling.
Poor local economic data, with retail sales data for September recording another monthly contraction, and a return for demand for safe-haven currencies like the dollar in recent sessions, ended the rand's run to an eight-month high as risk clouds gathered.
Following this afternoon's rates decision, where the Reserve Bank is expected to keep rates steady at 3.5%, come credit ratings reviews by Moody's and S&P on Friday.
Both firms already rate the country's debt at subinvestment, but S&P has the country on a stable outlook.
Moody's and Fitch already have South Africa on negative outlooks. Should S&P bypass an outlook change and move straight to a downgrade, the rand could suffer some steep losses, analysts said.
(Reporting by Mfuneko Toyana; Editing by Toby Chopra)