City have managed to win only one of the last four games in the league and they could lose their spot in the top four to local rivals Manchester United who sit two points behind with a game in hand.
Outgoing manager Manuel Pellegrini has copped some slack for City's disappointing domestic campaign but French defender Sagna feels the Chilean should be exempt from blame.
"It's very disappointing, especially with the way we started the season," said Sagna. "But we are to blame.
"We had everything in our hands to be the best and I believe if we play like we did against Arsenal we are the best team - but we have to play like this all season.
"But this is the past now and we have to keep our heads up. We can still make it happen.
"We have to recover, work well during the week and take the three points against Swansea. Then we will see what happens with the other results."