The City manager looks likely to carry out his threat to field a weakened team for the fifth-round trip to Stamford Bridge.
Pellegrini is concerned about the workload on the fit members of his injury-ravaged squad at the start of a week which includes a Champions League trip to Dynamo Kiev and the Capital One Cup final at Wembley.
"When young players have the opportunity, they must take their chance," said Pellegrini
"The team we are going to play against Chelsea will give young players a chance.
"They must take the chance in the correct way to show why they are so near to the first team and try to get the trust of the manager."
City had wanted the tie played on Saturday because they have made plans to travel to Kiev on Monday ahead of the first leg of their last-16 clash against the Ukrainian club on Wednesday.
That could not be accommodated for police reasons - Chelsea's neighbours Fulham are at home on the same day - and because the BBC requested to televise the game.
With a lengthy injury list that has already reduced him to 13 fit senior outfield players, Pellegrini feels he has no option but to rest some of his star names.
Goalkeeper Joe Hart will step down for Willy Caballero, as in all domestic cup matches this season, while Vincent Kompany, Yaya Toure, David Silva and Sergio Aguero are also among those likely to sit out.
Kelechi Iheanacho, hat-trick hero in the fourth-round win at Aston Villa, is set to start while other youngsters in the reckoning include recent matchday squad members Cameron Humphreys, Bersant Celina, Brandon Barker, Aleix Garcia and Manu Garcia.
City are still challenging in four competitions but Pellegrini does not believe any team is likely to win the quadruple under the current fixture system.
One of the Chilean's chief gripes is that a prolonged FA Cup run requires Barclays Premier League games to be postponed, but these can be difficult to fit in around Champions League fixtures.
He said: "For the moment, nobody can do it
Maybe one day, someone will but something is not right
You don't have the squad for four competitions
If you go far, you don't have time to play."
Pellegrini claims team selection this week will be one of his hardest tasks.
He said: "It's a big problem
It's not so big if we could play Saturday, but it's a big problem."
Chelsea, who played their Champions League last-16 first leg last week, are no longer involved in the title race or the League Cup and have no such issues.
Pellegrini said: "Chelsea have improved a lot (during) this season
They will play with a strong team."
Source : PA
Source: PA