Lyon, whose Ligue 1 game at Metz had to be abandoned in the first half after the hurled missiles deafened Lopes, were shaken by the incident which left him in hospital.
They are third in their group on seven points, three behind second-placed Sevilla and, after a 1-0 loss in the first leg, a win by a two-goal margin would take Lyon past Spain's Europa League champions and into the last 16.
They cannot be leapfrogged by bottom side Dinamo Zagreb, who travel to already-qualified Juventus.
Lyon, however, seemed badly affected by Lopes having to be sent to a hospital on Saturday night after a couple of the firecrackers exploded near him.
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"The eardrums were not damaged but he is suffering from traumatic deafness," Lyon said in a statement on Sunday while Lopes added on Instagram that he would need two weeks of treatment.
It was not clear, however, whether Lopes would be fit for Wednesday's clash.
"Lyon underline the fact that the whole squad... have been seriously shaken emotionally by this aggression," the club statement added.
Lyon, who played the Champions League semi-finals in 2010, will be relying on the in-form Mathieu Valbuena to take them into the last 16 for the first time in three years.
After a timid start to the season, the France international has been in good form lately, scoring two goals in his last two appearances.
Sevilla, third in La Liga, geared up for the clash with a 2-1 defeat at Granada last weekend and they will need to be fully focused if they are to reach the last 16 of the Champions League for the first time since 2010.
Sevilla still have a slim chance to finish top of the group as they trail Juventus by one point.
"I think we were a bit distracted by the Champions League," said midfielder Vicente Iborra.
"We could not show the best side of us," coach Jorge Sampaoli added.
Sevilla will be boosted by the return of influential midfielder Samir Nasri, who took part in training on Sunday after missing two games with a muscle injury.
(Reporting by Julien Pretot; Editing by Ian Chadband)
