Ivory Coast international Doumbia has scored four times in as many appearances to help his side to second place in Group B, including both his side's goals in September's 2-2 draw with Tuesday's opponents.
He will sit out the return meeting after his dismissal against Trabzonspor last time out but Slutsky has backed Vagner Love, available in Europe amid a three-match domestic ban, to fill the void.
"The absence of Doumbia could affect our approach," said Slutsky in comments reported by L'Equipe. "He is a big asset to be without but we have the weapons to adapt.
"And his absence does not worry me unduly because I think Vagner will be up to speed. He has worked hard, he is in form.
"We know he has to be right in his head and I think that is the case."
The Russians are level with Trabzonspor on five points, four behind Inter and three ahead of Lille - who need a win to keep alive any hopes of advancing in the tournament.
But Slutsky continued: "We also have to win to qualify. We are in almost the same situation and we are playing at home.
"I think both teams will come out firing, we must be ready to respond to the challenge."
CSKA's injury problems are easing, with Keisuke Honda and Sekou Oliseh returning to first-team action in Friday's league defeat to Rubin Kazan and Alexei Berezutsky having trained fully on Monday.
However, a recurrence of a knee injury has seen Zoran Tosic join fellow winger Mark Gonzalez, keeper Igor Akinfeev and forward Tomas Necid on the long-term injured list.
Lille's departure for the game was delayed by fog, forcing them to cancel both their training session and their scheduled press conference tonight.
Director general Frederic Paquet revealed they will face no sanction over the latter, telling L'Equipe: "We spoke to (UEFA), there is no problem."
Of greater concern, though, will be the lack of any opportunity to familiarise themselves with the Luzhniki Stadium's artificial pitch until the day of the game.