Brent crude is trading almost $10 below the $60 per barrel level that the Russian central bank has said could lead to the economy shrinking as much as 4.7 percent this year.

Sanctions related to the Ukraine conflict have shut Russian companies out of global capital markets.

The rouble has lost 8.3 percent just since the start of the year－after a 46 percent slide in 2014.

While S&P signaled last month it may drop Russia below investment grade within 90 days, traders of credit default swaps already treat the nation as junk.

If S&P does downgrade Russia, all of the country's assets will feel the pain, said Tatiana Orlova, chief economist for Russia at Royal Bank of Scotland Group Plc in London.

It may have a contagion effect on other markets, the second-most accurate forecaster said.

RBS, which last month predicted the rouble at 55 to the dollar in the first quarter, is reviewing that prediction and will not exclude further weakness, Orlova said.

She does not expect the central bank to sell dollars or raise interest rates further. Instead, the government may put pressure on exporters to sell their foreign-exchange holdings.

The yield on the government's rouble-denominated notes due in August 2023 jumped to 16.2 percent on Friday from 8.38 percent at the end of June.

Not everyone is lowering their rouble outlook.

HSBC Holdings Plc, the third most-accurate rouble forecaster in the rankings, is keeping its quarter-end prediction at 59.30.

"The situation in the oil market is very fluid and we have yet to see the full impact of the recent central bank and government measures on the rouble," said Murat Toprak, an HSBC strategist in London.

While the rouble may weaken to about 65 per dollar, it will then appreciate gradually, RBC Capital Markets analysts Daniel Tenengauzer and Daria Parkhomenko wrote in a note to clients on Thursday.