Former England defender Richards, who made his debut for the club in 2005, has rarely featured under Pellegrini, kept out of the side by Pablo Zabaleta and further marginalised by the arrival of Bacary Sagna from Arsenal.
Sweden international Guidetti has not played a league match since joining in 2008, while Sinclair was sent out on loan to West Bromwich Albion last season.
"We'll see what happens in the next 48 hours, they know they are not part of the squad because we have enough players for the squad but I don't have any news about them at this time," Pellegrini told reporters ahead of Saturday's Premier League match against Stoke City.
The Chilean said striker Sergio Aguero, who has netted in both City's league wins this season over Newcastle United and Liverpool after coming on as a second-half substitute, was fit to play after photos appearing to show him in pain during training on Thursday.
"Just Alvaro Negredo is injured but the rest of the squad have no problems - Sergio Aguero is absolutely fine," Pellegrini said.
"Eliaquim Mangala is not in the squad for tomorrow but Kun (Aguero) is - we'll see tomorrow how many minutes he will play."
City have been drawn with CSKA Moscow in the Champions League group stage for the second consecutive season and Pellegrini said he hoped the Russian club had learnt lessons after being given a partial stadium closure following racial abuse by fans directed at midfielder Yaya Toure.
"I hope for Moscow it is a lesson that they learn about that and hope that we don't have any problems, not only with Yaya," he said.
"I remember what happened last year. The pitch was also a problem, we played on a very bad pitch.
"But I hope Moscow have learned their lesson and we won't have any problems."
- Sports & Recreation
- Sergio Aguero
- West Bromwich Albion
- Pablo Zabaleta
- Bacary Sagna