City are still in contention to win four trophies but their form in the two weeks since they confirmed Guardiola's arrival in July has raised questions about their ability to mark Pellegrini's departure with silverware.
Successive home defeats by leaders Leicester City and second placed Tottenham Hotspur have left City six points off the pace with serious doubts about whether their expensively-assembled squad is still playing for the manager.
Backed by the wealth of Sheikh Mansour of Abu Dhabi, City are proving that all the money in the world cannot guarantee success on the field.
Pellegrini, who guided City to the Premier League title and League Cup victory in 2014, was honest enough after the 2-1 loss to Spurs on Sunday to admit his team had been beaten by the better side.
He defiantly suggested, however, that they could still win the title even though they have taken only one point out of 15 this season from matches against Leicester, Spurs and Arsenal, the three teams above them.
"We will see at the end of the season which is the best team," he said, "but the first problem is our team.
"We need to improve on a lot of things. We have 36 points more to play for. I think all the teams will lose more points from now until the end of the season but when you don't depend just on what you do of course it's more difficult."
City have a number of world-class players on their books, including striker Sergio Aguero, midfielder Yaya Toure and defender Vincent Kompany who returned to the side against Tottenham after six weeks out injured.
"There is not a chance we will give up on the title. We have to improve," said Pellegrini.
They need to do so quickly.
City face rejuvenated Chelsea in the FA Cup fifth round at Stamford Bridge on Sunday before a taxing trip to Ukraine and the first leg of their Champions League round of 16 tie against Dynamo Kiev.
Four days later they play Liverpool in the League Cup final at Wembley and meet the same opponents at Anfield in the League three days later.
Adverse results over the next two weeks could signal the end of a four-pronged trophy assault and condemn Pellegrini to a painful farewell before Guardiola arrives with a huge task to rejuvenate the club. (