The Premier League champions are looking to trim their squad before the close of the transfer window, with the Serbian defender now considered the fifth-choice centre-back
Goal reported in July that Nastasic has attracted interest from Roma, Inter and Fiorentina and Pellegrini admits that the Premier League champions have received offers for the 21-year-old, who is now considered the club's fifth-choice centre-back.
"Matija needs to play. We already have important players here with four full-backs, [Martin] Demichelis, [Vincent] Kompany, [Eliaquim] Mangala and [Dedryck] Boyata," Pellegrini told the press.
"So we will see in the next few days what happens with Nastasic. He is an important player but he has offers and I think the best thing for him is to play.
"We will see what happens but we have until the end of August to see what kind of offers we get for Matija.
"That also goes for Micah Richards, who didn't want to continue here because he wants to play more - he had a contract to renew but didn't want it."
Richards is desperate to leave City, with one year remaining on his contract, and is expecting the Premier League champions to lower their €8.75 million asking price with Liverpool, Tottenham, Everton and Newcastle having shown interest this summer.
Guidetti, meanwhile, spent the second half of last season on loan at Stoke City but Feyenoord coach Fred Rutten admits that the Dutch club are keen on a move.
"So we have three or four players extra - Scott Sinclair and John Guidetti are also important players but I don't like to have so many in the squad," Pellegrini continued.
"I think 22 players is enough and they are all players who have a lot of quality. It is good for them to play."