Raul Rusescu converted a first-half penalty to give the Romanian side a slender advantage heading into the second leg but the Blues keeper was frustrated to lose despite not having often been tested.
"To be fair, I hardly made a save all game," Cech told ESPN. "They scored a penalty and they won so it's disappointing we didn't take our chances.
|9/2||Chelsea are 9/2 with William Hill to keep a clean sheet against Manchester United
"We had some chances but didn't score. We had some in the first half and had some blocked in the second half.
"We've made it hard at 1-0 but we know it's not a score we can’t overturn."
Boss Rafael Benitez lamented after the game that the penalty decision against Ryan Bertrand had been "soft" but Cech refused to complain about the referee.
"Whether it was [a penalty] or not, the referee gave it," he opined. "It's not important what I think, it's important what the referee thought and he gave it.
"I'm not the referee and, to be honest, in this situation it's very delicate. His decision was what it is."