Cech is likely to start on Thursday night as Chelsea target a quarter-final place in the Europa League, but the Czech stopper believes that their Romanian opponents have already proven that they are a strong team in the competition.
The 30-year-old told the club's official website: "It is surely not going to be easy. Steaua are a tough opposition, and they have plenty of experience with playing in the European Cups.
"In the previous round, they demonstrated their strength by knocking out Ajax. They had not done well in the first leg in Holland but did superbly in the home match. They erased a two-goal deficit and progressed on penalties.
"That shows they are very strong at home and we need to be extremely wary."
Chelsea progressed to the last 16 after they recorded a 2-1 aggregate win over Sparta Prague in the last round.