Second place in Group E will go down to the wire on Wednesday with Roma, City and last-placed CSKA Moscow all on five points ahead of the final matchday of the Champions League group stage.
City must beat Roma in Italy to clinch second spot, while Rudi Garcia's hosts could progress with a draw, as long as top side Bayern Munich do not lose to CSKA in Germany.
Roma drew 1-1 away to City at the end of September but, in the lead-up to that match, Pellegrini's men had only won two of their past six games in all competitions, while the Etihad Stadium outfit have won five straight matches ahead of Wednesday's clash.
"I have just asked the players to continue playing the way they are playing now," the Chilean said.
"I think that is the best way to try and qualify. This is a different situation to the one where we played against Roma in Manchester.
"The only request that I have for the players is to continue playing the way we are."
Roma enter the fixture unbeaten in five, including three victories, although they have not won in the Champions League since the first matchday when they crushed CSKA 5-1.
City are in their fourth straight Champions League campaign but have only progressed to the knockout stages once - last season, when they were eliminated by Barcelona.
