Milan - Roma midfielder Radja Nainggolan has warned anything less than a win against Bayer Leverkusen could prove fatal to the Serie A side's chances of ending a five-year wait to reach the Champions League last 16.
After a mediocre start to their campaign, Rudi Garcia's men sit bottom of Group E with just two points from three games.
With BATE Borisov and Leverkusen just one and two points ahead of them respectively, Roma's hopes of reaching the competition's knockout stages for the first time since the 2010-11 season are not over yet.
But defeat to Leverkusen would mean Roma would have to win their final two group matches - including away to leaders Barcelona - to have any chance of progressing.
With the city derby this Sunday it is a crucial week for the Giallorossi, who sit third in Serie A just a point behind leaders Fiorentina and second-placed Inter Milan.
But Belgian international Nainggolan said all thoughts of beating Lazio have been put to one side as they set about reviving their last 16 hopes at the Stadio Olimpico on Wednesday.
"We have to think about the Champions League game first, Wednesday's match is crucial," Nainggolan said after Roma's 1-0 defeat away to Inter on Saturday.
"We have to win if we are to have any chance of qualifying (for the last 16). Then we'll turn our attention to the derby."
Roma began their campaign in positive fashion, holding defending champions Barcelona to a 1-1 draw in the Italian capital, but struggles on their travels have complicated matters for Garcia's men.
Stunned 3-2 away to BATE, Roma dropped more points in a spectacular 4-4 draw away to Leverkusen last month.
Having gone 2-0 down at the BayArena, Roma hit four successive goals, including a brace from midfielder Daniele De Rossi, only to concede twice in the final six minutes.