In the global markets, the US dollar traded lower in early trade after former US Treasury Secretary Larry Summers withdrew himself from the race to be the next Federal Reserve chairman.
The bank says the rupee can reach 57-58 levels though the RBI may try to stem the volatility by starting to build reserves at 60.
The domestic currency spurted by 425 paise or 6.28 per cent in last five straight sessions.
After hitting a record low of 68.85 to the dollar last week, a Reuters poll suggests the rupee will stabilise at 66 to the dollar by the end of September, while technical charts also point to a period of relative calm.
A higher subsidy burden and lower growth will weaken the country's fiscal metrics, analyst Atsi Sheth said in the presentation.
The RBI has bought Rs 124.62 billion worth of bonds since its announcement on Aug. 20 that it would occasionally buy bonds to relieve some of the cash tightness in the banking system.
The central bank was seen selling dollars consistently when the rupee would approach the record low of 68.86 hit on August 28.
Goldman says the downgrade reflects the more difficult external funding conditions for Asia as markets increasingly anticipate Fed tapering and eventual exit from unconventional monetary policies.
The partially convertible rupee was trading at 65.87/88 per dollar.
In the global market, the US dollar swung between gains and losses in the early trade, but the currency was poised to notch a weekly advance after Syria-related tensions weighed on risk appetite and aided the greenback.
The Indian rupee slumped to a record low near 69 to the dollar on Wednesday on growing worries that foreign investors will continue to sell out of a country facing stiff economic challenges and volatile global markets.
The partially convertible rupee closed at 66.24/25 per dollar after hitting a record low of 66.30, and down 2.9 per cent from its close of 64.30/31 on Monday.
Policymakers stepped in late Thursday to calm markets.
The rupee slumped to a record low of 65.56 on Thursday and is headed for a sixth straight session of decline.
The partially convertible rupee dropped to a record low of 64.13 per dollar on Tuesday and was trading at 63.38/42 on Wednesday, weaker than its close of 63.25/26.
The 10-year yield was last at 9.27 per cent, up 4 basis points on the day, tracking the rupee recovery.
The rupee tumbled past 63.00 to the dollar, down about 2 per cent on the day and breaching the previous low of 62.03 hit on Friday despite a spate of measures in recent weeks by the central bank and government to defend it.
The Reserve Bank of India late on Wednesday unveiled rules to restrict how much its citizens and companies can invest abroad and announced additional curbs on gold imports.
The government on Tuesday announced hikes in import duties for gold and silver, but it has yet to unveil other details such as its plan to tax imports of non-essential items.
In January, India allowed fuel retailers to raise the price of subsidised diesel every month and asked bulk buyers to pay market rates.