Speaking after the game, Cech acknowledged that Barcelona dominated possession but praised his teammates' effort and focus.
"We can be proud of what we have done today," he told Sky Sports News.
"There was amazing quality in the team, everyone gave 100%. We are not used to playing 90 minutes without the ball. Mentally it is difficult to keep the focus.
"We have been brilliant all over the pitch, the commitment to defend and cover everyone, we had a bit of luck but everyone did as they were asked."
The return leg will take place at the Nou Camp next Tuesday (April 24).