City were well placed at the turn of the year, having moved level with Chelsea at the top of the Premier League table.
However, since then City have been eliminated from both the FA Cup and the Champions League, while defeats against Arsenal, Liverpool, Burnley and Crystal Palace have all but ruled out their chances of retaining the league title.
And ahead of the derby with Manchester United, Pellegrini said: “It has not been a good season.
???It was not so bad until the end of 2014, when we were top of the table and also had the FA Cup and Champions League.
“But in the last three months we have thrown it into the garbage.
“I think always for the fans it is important to finish as near to the top of the table as you can and that’s what we must do.”
City lie in fourth place in the Premier League table, nine points behind leaders Chelsea.
Meanwhile, Vincent Kompany has rubbished claims that City???s squad is too old and needs fresh faces.
The Belgian turned 29 on Friday, while Yaya Toure, Pablo Zabaleta, Aleksandar Kolarov, James Milner, Edin Dzeko and David Silva are all also senior statesmen within the group.
But Kompany insists major changes are not needed at the Etihad.
“This team doesn’t need -restructuring,” he said.
“I would say it’s more about refocusing. These criticisms about age come and go with form.
???If you are in good form and you’re having a good season, then people say it’s your experience that got you there.
“If you’re having a bad run of form, like we are now, then age is the problem.
???But I can only speak from what I see and, looking around the dressing room, I haven’t noticed that this team is coming to an end.”