Referee Lee Mason sent off City midfielder Fernandinho in the 32nd minute and the FA have alleged Frenchman Sagna's comment, which was later deleted, questioned the official's integrity.
"It is alleged that a comment posted on social media by the Manchester City defender constituted improper conduct in that it questioned the integrity of the match official and/or alleged and/or implied bias on the part of the match official, and/or brought the game into disrepute," the FA said in a statement.
Sagna, 33, has until Jan. 13 to respond to the charge.
(Writing by Ken Ferris; Editing by Greg Stutchbury)
