Watch out for this Russia downgrade risk

Russia has the highest concentration of debt issuers at risk of downgrade of any emerging market country, according to ratings agency Standard and Poor's (S&P).

Across developing countries in Asia, Eastern Europe, the Middle East, Africa and Latin America, Russia had the greatest concentration of entities – be they companies, state institutions or government -- poised for downgrades, according to a research paper from S&P on Friday.

"Falling commodity prices and increased geopolitical concerns gave Russia the highest concentration of potential downgrades, at 27 issuers," S&P said.

Countries and businesses across emerging markets that were at risk of downgrade were rated from AA-minus down to B-minus that had either negative rating outlooks or ratings on "CreditWatch" with negative implications.

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Rush hour traffic jams Ukrainian Avenue in Moscow.

Slated for a possible downgrade was the Russian Federation herself, whose current credit rating is BB+ with a negative outlook, plus 26 Russian businesses.

Russia's economy is expected by the World Bank to contract 2.7 percent in 2015 and relies heavily on exporting oil—the price of which has tumbled over the last year.

Many of the Russian entities listed by S&P as at risk of downgrade were largely commodity-reliant, with oil and gas firms Lukoil, Gazprom, Severstal, Sistema and Novatek among those with a negative outlook.

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Transportation firms Russian Railways and DME were also on the list, as were a number of Russian financial institutions, including Gazprombank and the Credit Bank of Moscow.

Bad for EM?

Looking at emerging markets as a whole, the gap between potential upgrades and potential downgrades appeared to be widening, a factor that S&P said was an "indicator of eminent stress." The gap at the end of May 2015 was wider than at the same time in 2014.

This gap previously spiked in emerging markets in 2009, following the global financial crisis.

-By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt.