The City captain, who picked up a knock in training ahead of the match, was at fault for Philippe Coutinho's late winner at Anfield.
However, Pellegrini insists that he did not think it necessary to leave the Belgian out as a precaution.
"He started the game because he is the captain," Pellegrini is quoted as saying by BBC Sport. "He made all the proof before the game, he said he was okay, and the doctor said that, so I don't regret that."
City return to Premier League action tonight at home to Sunderland.