Mohamed Salah fired home late on, in a game where Chelsea never looked like getting anything, going through the entire 90 minutes without a shot on goal.
But despite a second defeat to the Swiss side, Chelsea are still through to the knockout phase of Europe's premier club competition.
"We lacked a good start because as bad as we started that carried on for 45 minutes, The second half we improved a little," Cech told Sky Sports.
"The only positive we have is that we qualified from the group.
"Sometimes 10 points isn't enough to go through. (On this occasion) we have
gone through but it is the only positive because we did not play well.
"If you give your opponent in the Champions League the feeling that they can, they can - and you see that.
"We could have finished the game off, but our last touch was missing - it was not our day.
"We need to be better."