Sane has been linked with an exit from City this summer, with Bayern Munich having talked openly about their interest in the Germany international.
"Adama Traore makes a lot of headlines because of his pace and power but to step into a title-winning side, to replace somebody like Sadio Mane or [Mohamed] Salah – I do not think he is there yet," Mills told Football Insider.
"Somebody like Leroy Sane – possibly. He is coming back from injury and has been linked with a move away recently and could be surplus to requirements.
"He is young, a great talent and has experience. That would be more realistic but I do not know if Manchester City would sell to rivals."