Drogba was left out of Saturday's 4-2 win over Aston Villa after picking up a foot problem in training while Luiz had to come off in the first half with an ankle injury.
Boss Roberto Di Matteo is waiting to hear the full extent of both injuries and hopes to know more in the next couple of days. Drogba did not play in the first leg and the Blues boss has plenty of options in attack with goalscorer Salomon Kalou hoping to keep his place, while Fernando Torres has found his shooting boots.
"He had a knock on his foot in training and couldn't make it," Di Matteo revealed when quizzed as to why Drogba had not played. "He's another one we'll have to assess for the next 48 hours."
One or two other players picked up knocks against Villa on Saturday, while Di Matteo has again revealed he may make changes to keep his side fresh.
"We have a few niggling injuries and also I have to look at the freshness of the team as we're playing every three days," he added.