The Frenchman is under pressure after a poor opening two months of his time in charge of the Azzurri.
Al Hilal defender Koulibaly said: "Garcia is a great coach and needs time to adapt, as happened to other coaches in the past.
"The players are with him, I spoke to 2-3 of them and they confirmed it to me. They must continue to work as always and everything will be fine.
"I hope for him that the club will have the patience to make him work quietly."