The City captain has sustained a hamstring problem and could miss the trip to the Stadium of Light as the champions go in search of a third Premier League win in a row.
"With Kompany, we'll see tomorrow," Pellegrini said on Tuesday. "He has an injury to his hamstring - we'll see how long it'll be."
Fellow defender Matija Nastasic has also been ruled out with a thigh injury, potentially leaving the Chilean manager to pick from Dedryck Boyata, Martin Demichelis and Bacary Sagna at centre-half.
Pellegrini's side recorded an impressive 3-0 win at Southampton on Sunday, capitalising on Chelsea's draw at Sunderland to close the gap at the top to six points.
Chelsea welcome Tottenham on Wednesday knowing City are hot on their heels, but Pellegrini insists his side were always in the title race, regardless of the weekend's results.
"We were never out of the fight for the title," he added. "We have to play a lot more games and then are too many points to play for."
City host Everton on Saturday before a crucial UEFA Champions League showdown with Roma the following Wednesday.
