The Mali international does not feature in the plans of Sporting head coach Rúben Amorim for next season.
Sporting hope to find a solution for 28-year-old Diaby in the next transfer window. The Portuguese giants want to recoup the €4.5m investment made when they signed him from Club Brugge in 2018.
According to A Bola, clubs in the Orient have made lucrative offers to Diaby, but not enough to entice him.
Diaby is showing little interest in a move to China and his priority is to remain in Europe.
The attacker is wary of a move to Asia, fearing he would lose his captaincy of the Mali national team.
Diaby wants to lead Mali to the 2022 World Cup and for that reason will look to continue in Europe.
Besiktas have decided not to use their €5m option to buy after his mediocre performances for the Turks.
Diaby made 23 appearances for Besiktas in the Süper Lig, scoring two goals during his season on loan.