The Frenchman has seen his role slashed since the summer arrival of Xabi Alonso at Stamford Bridge, and he's rumoured to be open to an exit either in January or next summer.
Josh Acheampong has replaced Gusto as Alonso's choice at right-back, following a fresh injury to captain Reece James, and a reunion with Enzo Maresca at the Etihad Stadium could now be on the cards.
Maresca was linked with an offer on the 23-year-old back in August, but that did not materialise into a formal offer, and talkSPORT claim both interested parties are uncertain over the winter window plans at this stage.
Chelsea are also expected to demand in the region of £75 million - with Gusto under contract until 2030 - and neither City nor United will pay that much for a player who is not currently part of Alonso's set up.