City's caretaker manager Keith Millen is seeking left back cover to deal with an injury crisis at Ashton Gate.
Devon-born Sawyer has also spent a two-year period on loan at Exeter, making 62 appearances for the Grecians.
With Jamie McAllister out for up to six weeks with an ankle injury and Lewin Nyatanga also nursing a knock, Sawyer is likely to go straight into the side to face Peterborough on Saturday.
Source: BBC Sport
