Spanish publications Plaza Deportivo and Super Deporte suggest that City will sell the French defender to Valencia for £15m at the end of his season-long loan spell at the Mestalla.
Regarding the deal, Valencia president Jesus Garcia Pitarch told Super Deporte: "It's an assignment with purchase option.
"Hopefully he'll do well, feel happy and want to stay with us.
"We won't communicate the figures - it's a private aspect."
But it is understood that £15m is the figure for a permanent purchase which will see City lose a great deal on a player they invested so heavily in.