The Premier League champions were beaten 3-1 by a Steven Naismith-inspired Everton on Saturday to leave them 11 points behind leaders Manchester City after only five games.
Jose Mourinho's side turn their attention to the Champions League on Wednesday, as Maccabi Tel-Aviv visit Stamford Bridge, and Ivanovic has called for a significant victory to get them back on track this season.
"We need one big win to come back to our way. We are not playing as badly as the results are showing but we have to wake up," he told Chelsea TV.
"I think at the moment we are being punished for all our mistakes. The only way we can change is to work hard and be ready for the next game, so it is like a final and we have to play like a final.
"The next game is very important for us. It is a new competition and it is time to change all this situation. I hope we will start winning the games soon."
Nemanja Matic, who scored with a stunning long-range strike in Saturday's defeat, says Chelsea are not accustomed to enduring such poor runs of form - though he believes they deserved a point from the trip to Goodison Park.
"Of course we are not happy," said the midfielder. "Everybody is sad because of the result.
"If you saw this game, I cannot say we deserved to win but we deserved a draw.
"Chelsea are not used to being on runs like we are at the moment but this is the reality. We have to work hard to get our game back to the way we played last season.
"I really don't know what's happened but it's not good for us and we need to see what we can do better as a team."