City are scheduled to play their third match in Group D against CSKA at the Khimki Arena stadium, a ground that their hosts share with Dinamo.
However, UEFA ordered CSKA to stage their earlier home game against Viktoria Plzen in St Petersburg - 394 miles northwest of the Russian capital - because of the condition of the playing surface at the 18,000-capacity stadium.
"It is unbelievable that we can play on this pitch," Pellegrini said. "We must pray because if it rains it will be impossible to play.
"I think the most important competition in the world deserves a better pitch.
"I am surprised because they didn't allow the other game against Viktoria Plzen to be played here and I think that the person from UEFA who reviewed it shouldn't have given the authorisation to play here."
The pitch is in poor condition and rutted after heavy rain in the Russian capital, and matters have been compounded by the fact that the national U21 side have also been playing there.
The all-weather surface at the Luzhniki Stadium in Moscow is out of commission due to rebuilding work in preparation for the 2018 World Cup.
Bayern Munich lead Group D with two wins from two games, while City and CSKA each have three points from two games with Czech side Viktoria Plzen yet to register a point.
You can make your own mind up about the state of the pitch by tuning in to watch Manchester City tackle CSKA at 5pm on Sky Sports 3