The former Arsenal centre-back was expected to leave the Etihad Stadium in the summer but failed to agree a move to Bursaspor.
City boss Roberto Mancini signed 19-year-old Matija Nastasic from Fiorentina at the end of August, meaning Toure's playing time has been limited.
The Ivorian said: "Joleon [Lescott] and Vincent [Kompany] have been fantastic and deserve their place, but it's much harder when a young player comes and steps in front of you.
"Since I came back from the problem I had, I've been fourth-choice every time and that's been really difficult. It's hard to come in and give your best.
"Sometimes I am not on the bench and that is not easy, but it's up to me to prove to the manager that I am still one of the best."
Toure was handed a rare start in the Capital One Cup defeat to Aston Villa on Tuesday.