The Frenchman went to Juve on a free transfer last summer, but has failed to secure a regular first team spot.
Now he is unhappy in Turin, and wants a move.
He would be moved on for a significant fee, or sent on loan to free space on the wage bill.
Juve would like to use him as a makeweight in a transfer deal, such as one that gives them Paul Pogba from United.
But if they cannot make that happen, they are happy to sell the player as he has not hit the expected heights in Serie A.