Goals from Yaya Toure, Fernandinho and Martin Demichelis put Manchester City into second place in the Premier League table as they continue their attempts to overhaul Chelsea
Chelsea and City remain the favourites to lift the title in May but Pellegrini believes it is still a four-way fight for the prize.
City overcame Fulham 5-0 at a rain-soaked Etihad Stadium to move six points behind Chelsea with 10 matches still to play whereas Jose Mourinho's side have only seven left.
"I don't think it's just between Chelsea and Manchester City," Pellegrini told reporters. "We must continue to consider what Liverpool are doing every week. They are playing very well and scoring goals.
"Arsenal, today, maybe had a bad game but they are seven points behind Chelsea with one game less.
"I think the four teams have exactly the same chances to win the title. Theres a lot of points to decide the title."
Liverpool maintained their title charge with a 6-3 win over Cardiff City in Wales and trail Chelsea by only four points but still have to face Mourinho's side and City at Anfield.
Arsenal are seven points from Chelsea at the top, meanwhile, after capitulating against Chelsea at Stamford Bridge.
A Yaya Toure hat-trick set City on their way to victory; the Ivorian converted a penalty in either half and curled a magnificent third outside the grasp of the impressive David Stockdale to take his season tally to 21. Afterwards he was hailed by his manager.
"He's a very important player, playing the way he likes to play," said Pellegrini. "Scoring 20 goals from midfield is not easy."
Fernando Amorebieta conceded both spot kicks and was booked for each meaning Fulham played a large part of the second half with only 10 men.
The Londoners were unable to keep out the strongest attacking side in the league as further goals from Fernandinho and Martin Demichelis condemned them to a dismal defeat. They are rock bottom on only 24 points and only seven games left for Felix Magath to save their season.
Next up for City is a trip to Old Trafford on Tuesday before facing Arsenal away next Saturday. Pellegrini said that although he savoured the win against Fulham, it was time to look ahead to the meeting with their city rivals.
"The derby is a special match so we must try from tomorrow to forget about what we did today and start thinking about what we must do against Manchester United."