Although Maurizio Sarri's new Chelsea isn't expected to move for another transfer, a potential Thibaut Courtois move to Real Madrid would see the Blues moving for his replacement, now thought to be Kepa Arrizabalaga.
England star Walker says their best is yet to come, with City boss Pep Guardiola demanding they go for broke by winning the Champions and Premier Leagues and both the FA and League Cups.
Tiemoue Bakayoko was present in games during Chelsea's pre-season but has left Maurizio Sarri unimpressed.
Mateo Kovacic's arrival on loan from Real Madrid has seen them all fall further down the pecking order.
Any loan deal for Bakayoko is likely to include an option to buy, according to Sky in Italy.
Bakayoko joined the Premier League side last summer as a replacement for Nemanja Matic, but doesn't fit into his manager's plans this term.
Chelsea travel to Huddersfield for their first game of the season on Saturday. But the nail in the coffin was not even being on the bench during Chelsea's recent Community Shield loss to Manchester City.
Courtois has been trying to force his way out of Stamford Bridge this summer after refusing to sign a new contract and Chelsea have made a decision to cash-in rather than risk losing him for nothing next summer. However, at AC Milan he could get regular football and possibly shine for his style of play.