Jerome Boateng netted a stoppage-time winner as City got their Champions League campaign off to a losing start at the Allianz Arena on Wednesday.
The reigning Premier League champions host this season's pace setters Chelsea at Eastlands on Sunday, and Sagna says that victory would provide a much-needed tonic.
"We kept working really hard until the end and it was a goal at the end but we had chances as well," he told the club's official website.
"We played against great players, one of the best teams in Europe but we defended as a team.
"We need to think about Chelsea now as we have a very difficult game on Sunday."
Sunday's encounter is scheduled to get underway at 4pm.