CSKA Moscow defenders Aleksei Berezutski and Sergei Ignashevich have been provisionally suspended from all domestic and European games.
The duo underwent a random doping test after CSKA's UEFA Champions League group stage match against Manchester United on 3rd November and both players' samples tested positive for a banned substance.
United and CSKA played out a 3-3 draw at Old Trafford but the pair's post-match samples showed up an illegal substance.
Both samples revealed the presence of a prohibited substance under the category 'S6. Stimulants' from the World Anti-Doping Agency Prohibited List 2009.
Berezutski, 27, and Ignashevich, 30, both regulars for the Russian national team, have been provisionally banned from playing in any friendly or competitive fixtures.
The UEFA Control and Disciplinary Body will meet to discuss the case further on Thursday 17th December.