The Ivory Coast international has not featured for the club since suffering an injury during his side's 3-2 defeat to Liverpool on April 13.
When listing his injury list, Pellegrini failed to mention Toure, but he did tell reporters: "We have [David] Silva, Jesus Navas and [Matija] Nastasic out with injury - all of the other players are fit.
"David is working, improving. With Navas's ankle, it's the same. These three players are injured - we don't know how much longer for David."
City are currently third in the Premier League table, six points behind leaders Liverpool with a game in hand.