CSKA's last European game against Viktoria Plzen earlier this month was moved away from the Khimki Arena because of the poor state of the surface but despite heavy rain in the Russian capital in recent weeks, the stadium will host the City match.
"I think it is unbelievable that the most important competition of the world is allowed to play on this pitch," Pellegrini told a news conference.
"We must pray tomorrow. If it is raining I think it will be impossible to play."
City meet the Russians with the sides level on three points from two games in Group D, three points behind leaders and holders Bayern Munich.
Pellegrini said he had examined the pitch, which is heavily sanded and bare in parts, and could not believe what he saw.
"I think it (the fixture) deserves a better pitch."
His CSKA counterpart Leonid Slutsky, whose side have lost five of their last seven games in all competitions and have not played at the Khimki stadium since August, agreed the state of the playing surface was problematic.
"I suppose the quality of the pitch is, absolutely, equal to the quality of our latest results," local media quoted him as saying.