City and Chelsea are considered favourites to finish top of the table this season, with Jose Mourinho's men currently six points clear of the 2011-12 champions having played three games more.
However, in-form Liverpool are also firmly in contention - four points behind Chelsea with a game in hand - and Pellegrini has refused to rule out Arsenal despite Arsene Wenger's side suffering a 6-0 defeat at Stamford Bridge on Saturday.
"I don’t think that it is just between Chelsea and Manchester City," said Pellegrini after City recorded a 5-0 home victory over Fulham.
"We must continue concentrating on what Liverpool are doing every week because they are playing well and scoring goals.
"Arsenal made a bad game but they are still seven points behind Chelsea, but with one game less.
"So I think the four teams have exactly the same chances to win the title.
"They (Chelsea) must play seven games more, Arsenal (and Liverpool) must play eight, our team must play 10 games more.
"That's a lot of points at the moment to decide that the title will be just for the two teams."
Pellegrini only had one fully-fit striker - Alvaro Negredo - for the win over Fulham after Edin Dzeko missed the game due to illness, although Stevan Jovetic was on the bench after a recent hamstring injury.
City's boss is hopeful of having Dzeko available again for the Manchester derby on Tuesday.
"I hope (to have him back) but at the moment I don't know," he added. "He felt sick. I think it's not serious but we'll see tomorrow (Sunday) morning."
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