The Blues travel to Old Trafford in the quarter-finals of the cup on Sunday as they bid to keep their hopes of lifting the trophy alive.
But ahead of that trip is their visit to Romania to face Steaua in the last 16 of the Europa League as one of three English sides left in the competition.
Manager Rafael Benitez could rest some of his stars on Thursday with one eye on the United clash but keeper Czech is adamant the players must be focused on Steaua.
"We cannot be thinking of Manchester when we have an important Europa League match ahead," he told his official website.
"We need to take it step by step because each game is important for us. The manager has to think into the future but us players, we always concentrate on the one upcoming game."
Steaua are not among the biggest names in the round of 16 but Cech insists reigning Champions League holders Chelsea cannot afford to take them lightly.
"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," he said.
"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."